"I told you never to mention or imply that darned thing again, I want none of that devil fruit power bullshit, I can manage all by myself!" he said suddenly becoming very tense

"It's been how many years? Five years? Don't you think it's time to see it as something other than some wicked curse?" he argued, true that he knew what kind of influence buried within that disciple of his but being a scientist and a doctor he was still curious about it. Not many people can produce acidic chemical as they wish and Leo can. It's just too good to be ignored, just imagine what kind of fighting style or concoctions' ingredients can be developed from it?

"If it hadn't been for this fruit, this exact power, my father would have still been alive right now" Leo retorted

"Who knows, maybe yes maybe no, the fruit would have still been on that ship and Shiki will still sink the ship and everybody dies! Knowing your father (not really) he would have sacrificed himself either way! Come on if you let me help you I think I know what you need" argued the doctor.

"What about the devil that you've been theorizing about? What about him? Did you remember the time when I went berserk 5 years ago? You want that to happen again because I don't know whether I can hold him this time or not!"

The doctor was speechless "I thought that guy's gone when I gave you the bracelet"

"Locked away not gone, he came back to me months ago when I was in the cave, telling me how I should 'let him go'" the doctor dropped whatever he was doing in the kitchen and came to the middle room

"Why didn't you tell me about this earlier?"

"I've been planning on telling you, but I thought you wouldn't be this hyped about my power so I thought…you know, it could wait"

"I didn't know, I'm sorry"

"Forget about it" Leo said as he reached forward to grab anything to distract him from this unwanted conversation but can't seem to bring himself to get it out of his mind. The doctor was still sitting beside him, looking more concerned than ever, and probably feeling a bit bad about bringing this topic up.

This is why he didn't tell him earlier, he'd just overreact and felt like it was his responsibility to cure whatever sickness or oddities Leo has "But you know…I didn't think he show himself up to me that night without a reason"

"What do you mean?"

"It was the day before I discovered my haki, he seemed to know that sooner or later I was going to discover it, I don't know but I've been thinking…what if he's afraid of haki? But that doesn't make sense does it? How can I hurt something so deeply rooted in my mind?" the doctor seemed to be fascinated by this, yes, I think I could see the connection here.

"Leo, I haven't told you this but haki like sea-stone can cancel abilities" Leo's eyes lighted up at that, no wonder! He was afraid that I'd lock him up there forever with my haki

"How does that work?"

"Hatsu? I don't know how that works but in fights against DF users I always have that on my mind 'cancel their abilities' and it did"

"Can you use Hatsu on yourself?"

"Honestly, I don't know"

"Well then there's only one way of finding it out" Leo suddenly got up from the couch and walked outside, the doctor knowing what his son's intention was followed closely behind.

"I know you want to lock this guy away as long as you can but I can't guarantee it'll work Leo, haki is a complicated art, one guy could master one technique in a minute while it could take another guy one month, you're gambling here" but Leo has already taken off the bracelet by the moment the doctor finished voicing his concern, he just grinned "Remember what you said to me when I was a kid and I couldn't sleep because I was afraid of darkness? You sat down and said to me, 'well boy you can't live the rest of your life fearing the darkness can you?' Well I feel like this is the time to confront it and if I lose, then that means I don't deserve this power, it's that simple" the doctor just stood there, acknowledging the choice that his son has made, for a moment there the doctor thought he saw his father Len, his haki, it'd felt like his.

When he said that to the doctor it had sounded like he was a brave guy or something but deep down he still have his doubts. All he could do now is to wait and when the time comes he's going to be ready with his haki.

"Well?"

"No, not yet" but then as soon as he said that he felt a sudden surge of power inside him, it felt like he's just been struck by a lightning that energized him and made him invincible. But it wasn't his haki, no he would have felt it, it was something else. "No, it's too much!" Leo groaned as he felt the new power that he was holding overwhelming his ability to control it. The power kept coming in while Leo's own haki was already stretched to its limit.

"Leo! What's wrong?"

"It's the devil, he's trying to replace my power with his!"

"Leo remember, your haki! Use it!"

"It's not enough, I'm losing!" Leo said as he felt something changing, changing him from inside, something foreign.

"W….WHAT the..." the doctor could only say that as he watched his son turned into somewhat a gooey New World-ian abomination, his skin turning liquid green. His face melting, his eyes were gone, what was left were the two sockets that used to house his eyes, the same happened to his nose while his mouth has completely gone, there weren't even a line. Leo's face looked more like a mouth-less skull now than a normal face of a human being. He didn't know what else has changed since his clothes were still there albeit a viscous acidic one. Yes, acidic, as he saw the drips from Leo's white tank-top dissolving the grass below him.

"Alright enough! Wear your bracelet now Leo! LEO!" the doctor ordered him, a note of urgency in his voice.

"This is GREAT!" the manifestation of Leo's power exclaimed, so he did have mouth, but it was more like a hole now, with acid dripping from it. There seemed to be no teeth or tongue inside, just a hole.

"Leo, we'll be found!"

"No you don't understand father, this is so GREAT! The power is nothing else that I've ever felt! See this!" Leo swished his hand and spattered the green liquid on a tree trunk "Wait for it, it's getting to the best part" the doctor's eyes widened as he watched the little green splatter pattern on the trunk of the tree began to expand to other parts of the tree and the tree began to crack and changed colour. Minutes later there was no longer a tree or anything else for that matter, the thing has dissolved the thing effectively from the tip of the highest branch down to its deepest roots leaving a gaping hole on the ground. The doctor could only watch in awe, this power was of different level than what Leo had exhibited 5 years ago. Back then his acid was nothing more than a ticklish substance, the worse you could get from its contact was a minor rash.

"Leo stop it now or you'll destroy the entire forest!" the doctor began to think that Leo has lost it

"Why would I stop!? This is great, this power I feel like I can conquer the world!" the doctor just stood there dumbfounded, Leo would never say those things.

"Remember what they do to ability user here? You don't want to create a problem for yourself here Leo, think about it" the doctor tried to remind Leo, hoping that he'd just calm down and talk sense again, but now Leo looked at him with a pair of hateful eyes instead, the expression it was like he was standing face to face with his nemesis "IT'S YOU AND THIS STUPID COUNTRY THAT ARE THE PROBLEM! YOU'RE JUST A HINDRANCE!" Leo yelled while pointing his finger at him as he got nearer to him, the doctor could only take a step back "I was doing what's best for you!" "WRONG! YOU JUST DON'T WANT TO SEE ME STONGER THAN YOU! YOU'RE AFRAID I'D SURPASS YOU! YOU'VE BEEN TRYING TO CONTAIN ME FOR SO LONG BUT I NEVER FORGET WHO MY REAL DAD IS! I'D NEVER BECOME A MARINE LIKE WHAT YOU ALWAYS WANTED ME TO BE! I CAN FEEL IT NOW, THE RAGING PIRATE BLOOD IN ME! WITH THIS POWER I'M INVINCIBLE!" Leo swung his leg and kicked the doctor, the surprised man barely had enough time to harden himself with his haki. However, the kick was strong enough it threw the doctor several meters onto the ground. The doctor looked around quickly and found a wooden stick before he did a kip up and swung it at his delusional son. But nothing happened. The stick, it went through Leo, making an open diagonal wide gap between Leo's chest and stomach. The doctor threw the stick away to the ground as Leo's acid started to make its way toward the startled doctor's hand, dissolving the rest of the wooden stick in its wake. Leo just laughed "TRY AGAIN OLD MAN!" Leo thrust his leg straight forward as he did a snap kick aimed at the doctor's chest. The doctor had to admit he trained his son good as it was enough to break his haki, but not enough to make him tumbling into the ground.

"Satisfied?" the doctor taunted the disgruntled Leo "I HATE HAKI" knowing that he could never use his haki whenever he's in this form. "Now's a great chance to prove which one's stronger, haki or a logia?" the doctor continued to taunt Leo.

Leo continued to kick and punch the doctor to no avail, the doctor's haki were too strong to penetrate. But that didn't mean Leo was no match to the doctor as he set up great defense that even the doctor found it difficult to find an opening. It didn't last long though as the doctor started his attack with a powerful spinning heel kick to the head, imbued with haki of course. The kick managed to throw Leo a few meters into the wood. Good, less people will see this. Thought the doctor.

Leo, on the ground opened his eyes and groaned as he felt his head spinning from the last kick. He quickly got up and looked around not seeing his foe anywhere among the vast expanse of wood before him "told you, haki is superior than mere devil fruit ability" Leo turned to see where that voice was coming from but by the time he did so his face was already met with another kick. His flying body destroyed a few trees as he went.

"WHERE ARE YOU!" Leo was getting frustrated, what seemed like a great power minutes ago now seemed worthless when faced with the doctor's haki in this wood. This is what he wants me to do, to fight him in the woods! That bastard. Leo ran toward a nearby clearing to at least lessen his foe's advantage. The doctor knowing his foe's intention moved in for the kill, knowing fully well that by doing so he was exposing himself. But he took his chances anyway.

At last Leo saw something moving in the corner of his eyes thanks to the moonlight escaping from the nearby clearing ahead of him. "YOU SLIPPED!" Leo threw a punch toward the figure but the doctor intercepted it just in time, he pulled Leo's right hand and hit him on the gut with another one of his heel kick. It hit the spot where the bald guy months ago had previously hit him. Leo groaned as he fell to his knees, not wanting to give his foe time to recover the doctor hit him again with one last powerful snap kick, now to his chin to ensure a knockout. Leo dropped to the ground, arms splayed wide and the fight was over.

As the doctor walked around him to put on Leo's sea-stone bracelet again, Leo turned back to his 'human form'. The doctor just shrugged his head, he didn't know what the hell happened just now. He's never fought like that since he left Grand Line. He certainly missed those times where he'd beat down over-confident devil fruit users who thought he was just another 'scientist', boy were they wrong! And somehow looking at Leo here, reminded him of those people. It's his worst dream, truly to see Leo turned out to become like one of those Pirates. This is why he brought him up in this quaint little town, where his father grew up but he was a 'special case' as the elders of the village told him. Looking around at the destruction that their little fight had caused the doctor sighed, he didn't know if he was serious or not about 'conquering the world' but he was sure if he hadn't been able to stop him earlier without a doubt he'd cause quite a destruction to the world. This he can't let that happen, not now, not ever, now he knew Leo still need more time to be trusted with his acid power yet.

It was raining outside as Leo regained his consciousness. He looked around and find that he was tucked comfortably inside his bed. "Ouch" Leo felt a sting in the side of his head and realized that his bodies were wrapped with bandages here and there. "What the heck happened?" as he raised his hand to soothe his aching head he caught sight of his sea-stone bracelet on his wrist and it all came back to him, the event of the other night, him taking off the bracelet and fighting the doctor…and lost "Uh oh"

"Ah Leo, how are you feeling?" Leo turned his head to see the doctor standing in the doorway with a fresh bowl of soup, despite last night's fight the doctor seemed to be as healthy as ever, there were no bruises or even scratches on him. Leo sat up on his bed and took the bowl of soup "I…I'm sorry" the doctor just smiled and sat beside him on the bed "Let's save that for later, now it's better for you to rest" the doctor stroked his son's hair "I'm just glad that you're alright" the doctor stood up and left, closing the door behind him. Leo could only curse at himself for letting the devil overwhelmed him like that, why do I have to be so weak…

Night

"Well I do believe that the greater the power is, the harder it is for the user to control" the doctor at last shared his comment during dinner after many attempts made by Leo to make him talk about what he knew and learned from last night's incident. He needs to know every single detail, what caused it to happen, how to stop it, he can't let his life be haunted by a ghost he know could control him at any second.

"And being a logia is greater than other type of devil fruits?"

"It depends, but I do believe that it gives you greater power from the get go while in the case of paramecia you need a lot of creativity to make it effective, some zoans too as they can shape-shift into different types of the same animal, I've seen these kinds of zoan-users before and most of them were efficient fighters who've perfectly adapted to their own forms, but then again they're rare…most were confident with their extra-strength they didn't bother to expand it"

"How did you know that I wasn't just a paramecia who happen to be capable of producing acid?"

"At first I thought you were a paramecia too because honestly there aren't many logias out there but last night you've proven to me your fruit is of different class than paramecia" Leo looked confused, well it couldn't be helped since this was the first time the doctor explained the world's general knowledge of the devil fruit to him "Your body Leo, it was completely liquid, you know what that means right? Yeah you're invincible except…" "Haki" the doctor just nodded passively, he was still sorry that his son had to learn it the hard way about haki's effect on devil fruit users. "Paramecia, no matter how much acid one can produce will never be able to turn himself into acid, but you could…Leo, you're without a doubt a logia"

"Being a logia, that sounds great, really father but it wouldn't be of use if using it means hurting you…or anybody else for that matter"

"That's why it's important to tell me what happened last night, from your point of view, what made you…gone berserk like that"

Leo paused for a second to think about it all, to recall what had happened that night.

Leo placed his mug in the table and started to talk "It was him…" Leo looked at the doctor to see if he understand what he meant "the power were too much for me to handle, it had felt like haki, I could feel it around my body but it was…more powerful, so powerful I couldn't do anything to stop it even with my haki, it kept surging into my body and I saw him approaching, forcing his way through my face and the next thing I knew I had these ideas and images in my mind, about how you've been isolating 'me' for these years, preventing me from developing my full power, stopping me from becoming what I really am? Then there were chaotic pictures about wars, a desert, the Marines, I saw a Pirate's Jolly Roger and a water…no…it was the sea, it felt like I was being dropped into the sea then there were random pictures…horrible flashes about me doing something that I'd never even think about of doing, there were strange creatures and prison bars…I don't know it was all jumbled up! Then before I realized it I was already attacking you, I was conscious, but I couldn't think straight, it…it felt like it was the right thing to do, attacking the man and the system who've been keeping me from becoming what I truly am…you must know father that I'd never think of you that way, you've done so much to me…you are and will always be my father…" Leo felt the doctor's hands in his balled hands "I know Leo, I know you'd never do something like that and listen…it should be me who's sorry because I was the one who forced you to do it…"

Leo shook his head "If I wasn't so damn weak…" the doctor squeezed his hands "Listen Leo, I've known you since you were 2 and I've been taking care of you, training you ever since and you know what? I know you're everything but weak isn't one of them Leo, you have to understand that. It's not you, it's just that there are some things that take time to get used to…what I can advise you to do about this is for you to train your haki to balance your fruit power…" Leo opened his mouth to protest but the doctor stopped him "…of course with the bracelet still on, the first thing you can do is try to get a feel of your haki body, the organs and vessels that produce and circulate the haki, you must have felt it inside of you when you released your haki, once you gain control of it release it slowly…because Leo the thing about haki is, you can get as much haki as you want, it's easy but the question is how much can you hold? See, you'd be feeling more than tired if you lost too much of your life force, believe me you don't want to feel it, so do it slowly" Leo's head raised, there were words that caught Leo's intention "What do you mean I can get as much haki as I want?" the doctor sipped his coffee "All this…is energy Leo! the earth, the nature, the air, do you know that energy is infinite, they can be neither created nor destroyed, do you know what that means? that means our world is teeming with energy and it's free for us to take!" Leo always knew the doctor was always a bit weird, how can energy be infinite? "Energy have many forms, they can change into a different kind of energy if put in certain circumstances, you don't feel haki in the air simply because there's no haki in the air, it'll be if you breathe it which your body will convert it into energy aka haki, same with eating and sleeping, that's why I said your health, your diet matter"

"Then if it's only a matter of what you breathe and what you eat then how come your haki is way bigger than mine? What did you eat to get that much?"

"As I said, you have to be able to hold that much haki to be able to control it, most people waste their haki to do their daily lives, some barely have enough haki because they don't have control over theirs, like I said months ago haki is affected by your feeling and what you think, while in order to maintain your haki you have to be as calm as possible and you can't let your emotions take you over. These emotions affect haki in many ways than you can imagine Leo, but I'm afraid if I explain about how this works it'll only bore you more…what I can say is practice, keep practicing the focused breathing techniques that I've taught you, apply that in your meditations and other forms as it helps your haki to circulate around your body and you'll find yourself with considerably improved haki"

"But how! How does it work? I don't think I can get it right if I don't know what I'm doing"

The doctor sighed, he didn't know how to describe it as he was only a medical doctor and all these words he said about haki was a direct explanation his trainer gave him when he was still in the Marine and he didn't give him a hell lot of theoretical information for him to rely on, he had to discover this by himself, you should be grateful that I teach you this at all Leo! But the doctor kept his cool and at last found a 'simple' explanation that his son would hopefully understand "Think of these forms as exercise, think of it as your strength training where you keep adding weights to build your muscle, you know to build muscle you have to break that resistance barrier right, same with haki training you have to set the bar higher than any other normal people by doing the right breathing techniques, and trying to keep your haki accumulated within your body by making sure that every part of your body is getting the same ration of haki by doing the right forms of mediation, over time the natural amount that your body can store will increase because it knows you can hold more this time and then you circulate the haki evenly around your body again, you then get more and more haki for you to practice and improve your Ten…keeping your mind calm is important here as it'll be difficult for you to feel the flow of your haki when you're distracted by something else" Leo was still a bit confused by the explanation but I think he got the gist of it. So it's some kind of resistance training…concluded Leo

"Alright dad, but can't say I got it all though…" Leo said as he stood up and took the plates to the sink

"Don't worry, you'll understand it when you practice, I know I did"

"Oh I can't wait to try this logia power of mine without the hang ups" said Leo clearly motivated, it might take him a long time to be worthy of his devil fruit ability but he could say it'd be worth the wait.

The doctor's eyes sparked seeing such young energy before him…the kid didn't know that with great power like that comes with it greater responsibility and also threat…from his experience devil fruit users will almost always end up as either a vigilante or criminal, thinking that they're special. That's one of the reasons why he must prepare him for the future, for the so called Great Pirate Age has no place for the weak. Everyone were so blinded by the opportunity of finding the late 'Pirate King's treasure they didn't realize they'd sunk lower than the Pirates before them, they at least still have some codes of honor binding them with Whitebeard being one of the last of those Pirates. Now it's not about adventure anymore, it's about who's going to be the next Pirate King, who's going to dominate who, the highest bounties and all that…"Just keep it in your mind Leo that whatever the reason is you can never show your power to anyone, you know this sea doesn't take ability users too kindly…"

"I know I know, you've been telling me that for like a billion times already! North Blue sure is a tough place for devil fruit users to live in and the irony is i can see why"

"When you become a Marine you can do whatever you like with that ability of yours" he said as a matter of factly. The least he could wish for his son was for him to not become some degenerate Pirate who's too confident about his ability, what good did being a Pirate do to Len? Well Marine or Pirate or anything else he knew Leo would become a powerful man. He'd make sure of that.

"Let's say I did overcome the curse thing, what good would that do if I can't even use it? You know that I'm not the adventuring kind of guy, I like this place, home sweet home"

The doctor just smiled "I'm not saying you cannot use it, just don't show them your ability" the words earned the doctor a confused look from his son.

"Wait…How am I going to use it without showing it to everybody?"

"Leo Leo Leo…my simple Leo" the doctor murmured with that smug smirk of his, obviously he knew something that Leo did not know about…he sighed, preparing himself for another lecture. "Do you know why people eat Leo?" Said the doc as he opened the refrigerator and grabbed two oranges "we eat so we'll not starve, so we'll not run out of energy right…?" The doc tossed the other orange to Leo who was still cleaning the dishes. "What people like you don't know is that our body doesn't need sandwich, it doesn't need cereal or vegetables, it needs the substance within, something that our body cannot synthetize or produce on its own" the doc said between his peeling and swallowing of the piece of orange. "Now these substances are acid…acid is not merely a liquid that dissolve objects, acid is actually a condition…so if you're really an acid man, then you should not only be able to create an acid that destroys but also to construct…the ones that are responsible for growth, recovery, metabolism and more importantly producing enough energy for your everyday lives…if you could produce them in an infinite amount within your own body you'd get an infinite amount of energy! This way you can use your ability without anybody noticing, this is what pushed me into suggesting you to take the bracelet off in the first place..ah…sorry to brought that up again, but of course it's just my take on your ability" said the doctor as he swallowed another orange.

"How do you know all this?" the doctor never seemed to stop impressing him with his wide range of knowledge, that he never even knew existed. He was sure that if the doctor was to teach him about everything he knows about these stuffs since he was little, he'd still be lecturing him right now.

"Let's just say I've done quite a lot of researches compared to other scientists my age"

"I thought all you do all day was listening peoples' heartbeat with that stethoscope of yours, and how old are you anyway? 80?"

"Don't be rude boy! I'm only a little over 60 so that means I can still beat you up pretty good if you mention my age again! And yeah I help people with their problem and I did some researches too, you'd know it if you haven't been so busy going to town stalking that beekeeper girl that your friends told me you liked!"

"Damn them!" Leo cursed at his friends, now that he thought about them, he kind of missed them all, this summer, they all went to some resort towns down south where it's warmer with their parents while Leo was stuck here being the doctor's errand boy as usual. The doctor said that he was not a 'summer guy'. Leo just sighed at his predicament.

But the doctor's explanation has made Leo realize something, his ability is a very versatile one but he felt that he was going to need lots of time to perfect it. Identifying and producing these 'good acids' he felt like trying to find his haki all over again. "With those matters aside I think it's indeed a very exciting theory doctor! One problem though…I don't know how to produce them, It seems like all I've been producing are the destructive ones…" "Well that's natural since you've only taken off your bracelet for once, and look how that turned out" Leo just shook his head as the doctor implied that incident again, he didn't know whether the doctor do that on purpose or not.

"It takes time Leo…you have to have a strong will to master a devil fruit, from what I see I think it's going to be a greater challenge for you than finding your haki…there are countless of devil fruit users who lost their lives foolishly because they don't fully understand their ability out there…this time you'll have to do it alone...while exploring your potential fruit abilities is good I personally think it's best for you to keep training your haki first, I'm thinking about setting you up with a different set of exercises this time"

Leo finished with the dishes turned around to face the doctor while drying his hands with a napkin "Yeah, this summer I don't think I have anything else to do anyway, you said something about your friend needing some help with something? Is the money good?"

So that's a preview of Leo's Acid ability, i have to admit by this point i still haven't decided what his fighting style will be, haki or devil fruit, if it was going to be devil fruit maybe you readers have any suggestions of what might his variations of 'acidic' power be as there are many kind of acids out there and i don't even think i know half of them. So if you have an idea i'd really appreciate it if you tell me alright?

Hope you enjoyed the story