Spoliers for the LN volume 15 ahead.

We are starting off right in the middle of volume 15 with whole Serena mess finally reaching it's conclusion, but for the sake of convenience I'm going to just straight up change some events that happened earlier in the main story.

Not to mess with the source too much let's just say three things. One: there is no upcoming attack on either the capital or the city of Axel. And two: Vanir didn't give Kazuma all those forbidden potions instead something else happened that is going to be briefly explained soon enough.
Also Serena didn't kill Kazuma, good for him right?

I apologize If that sound like an easy way out to you.

Without further ado, let's begin.

Change of Heart

Chapter 1: Encountering the Exploit.

"Why does my life has to suck so much?" Said Kazuma Satou, currently lying on his bed, still thinking about what happened earlier this morning.

Darkness finally managed to restrain Serena and the demon king general was now at the mercy of Kazuma and his companions.

All damage dealt to her will be returned to the attacker. This is a simple curse but just as it usually goes the simplest things are the most problematic as there is no catch that can be exploited.
No matter how we look at this situation, there is only one thing that can be done. I really don't want to do this, but there is no other way.

"Megumin please return the bottle to me."

"Oh no, you are not going to do something as stupid as making her drink this ridiculous potion."

"Megumin is right Kazuma, we can't afford to have you become even more useless."

You fucking toilet goddess, there is no one in this world more useless than you and that is counting those bat shit crazy maniacs you call your followers.

Leave my precious Axis cult alone you shit-NEET.

As we were arguing I noticed that Serena was frantically gasping for air. I could have guessed that this was going to happen. I looked at darkness, who have put her in a sleeper hold. Lalantina's face looked just like a certain "art" from Japan I was more than familiar with, which could only mean that our eroness was also fond of choke play. Darkness really was a lost cause but she was not the only idiot present in this room.

"Both of you seems to have forgotten what I said earlier, if she drinks this elixir both me and Serena will be reduced to level one wich means that she will no longer be able to act as the general of the demon king."

"But.."

"Megumin I understand but this is something I decided myself and I am ready to do it. This is the last time I do something self-sacrificially so let's just be done with it." Well maybe I shouldn't rise flags like that but I don't really care right now.

"If you really are certain about it..." With those words megumin gave me the bottle that was going to render me next to useless. I took it and moved closer to serena who was close to passing out from the lack of oxygen.

"So Serena let's see how this works on you." I forcefully opened her mouth and poured the entirety of the potion down her throat. Almost instantly I could feel some change about myself. It's not like my stats rose that much as I've been leveling up but some strength still left me as my level dropped down to one.
At the same time Serena finally lost consciousness, just as I thought in her case losing that many levels must have meant a significant loss of power. Well now she is as good as dead so that means we win.
With how troublesome her power was I really am surprised that I didn't die this time. Well she was going to chant some death spell earlier but darkness interrupted her just in time. For once she acted like a proper crusader and protected me I will give it to her but still... As I looked how disappointed she was now that serena's curse stopped working I just couldn't bring myself to thank her.

That's how it went with Serena, this whole thing was certainly unlucky but it was not the reason Kazuma was so upset right now. It was actually what happened a few hours later that got him in the bad mood he was in right now.

After serena was finally dealt with we gathered in the living room to discuss what to do next.
Now was the time to finally reveal why I was so eager to use this bullshit potion. It was all part of the greater plan I came up with.
With the defeat of another general the barrier around the demon king castle is going to weaken even more and Aqua could probably destroy it right now. What this means is that it's finally time for the final showdown with the main villain himself. Or at least it would have been if not for the fact that now I am pretty much a death weight. So first things first I should go and restore myself to the previous level before we can plan anything else.

"We should probably start with some easy monster hunt quest, let's go to the guild first" Said Megumin.

Of course girls were more than ready to help me.

"Don't worry Kazuma I can tank any enemy for you, even if it means being repeadly assaulted and mauled while you struggle to deal any damage and kill them." Darkness's face was getting red.

"Even if you die I will resurrect you so just hurry up Kazuma."

"I refuse."

"Hee, why? We have to act fast and kill the demon king so I can finally return to heaven." Aqua screamed.

"As if killing the demon king would ever be possible with you useless bunch. And now with me in this state it's beyond impossible."

"That's why I said to go do some quests so you can level up…"

"I refuse, I said again. I would rather go and find someone to level me up in a convenient way than stick around with you and be eaten by frog and other monsters.
In fact for a month I refuse to do anything regarding demon king in any way. During this time I will deal with my situation myself, I don't need any of you to help me with that."
He didn't lie but he didn't tell the full truth either. His plan was to get as fast as he can to the capital.

Once I get there I will hire some mercenaries or higher level adventurers to go and farm exp with. I'll meet with iris and persuade her to let me stay at the castle so that my safety is secured. Who knows maybe I'll even tell others that the barrier around the demon king castle is the weakest it's ever been and they will gather forces and go kill him themselves. Yes, this time I'm not going to put myself in danger, no matter what those three have to say.

Seeing that he is serious about this, megumin , refusing to give up so easily, tried different approach.

"Kazuma if you agree to go with us, I will give you a reward." As megumin said those words she lifted the corners of her skirt a little bit.

Kazuma gulped, couldn't say he was not interested in what megumin had to offer as he remembered the sight of her panties. And if this is something that finally lets them cross the line and become proper lovers then maybe he shouldn't turn her down just yet. To be honest just thinking about what a combo of steal and her lifting her skirt could do...

"Uugh look at this creepy grin. He probably fantasizes about something beyond perverted., you really are the worst you lolizuma"

"Oi who are you calling a loli Aqua?"

"Nope still not doing that, you will have to try harder than that to change my mind." He said, thinking that he could bargain for something better. If they are going to drag me through hell, then they better prepare themselves for something equally bad. Also who said I can't just roll with my plan while taking advantage of the three of them at the same time... Yes this is the ultimate plan, let's wait for the next offer, I can't show them that my resolve is weakening. Just as Kazuma was starting to enjoy this turn of events.

"Ok so what about..."

"Stop darkness, let's just leave him be. I have a feeling that if we continue this dialogue he will do something unmoral or straight up illegal to the three of us."

Fuck did I overdo it? And why is Aqua so witty and perceptive only when it's not convenient for me?

"Guess there is no other way, we will give him a month and then proceed to vanquish the demon king, if you are not a total trash then you will join us Kazuma but right now I'm not so sure about you."

Aqua's words surprisingly hurt him. Usually when they argued he didn't give a shit about her insults but this time was different.

"I guess you are right, as much as I don't like lying around doing nothing, I can use this free time to master my explosion so that the demon king won't stand a chance. Huh, guess this was asking too much of Kazuma after all."

"I'm heading home to discuss this with my father, it's better than seeing kazuma avoid his responsibilities and by using the influence of my family we can gather many allies to help us with our cause."

So it's decided, now you can go and lock yourself in a room for a month you shittNEET.

Kazuma was angry, in the heat of the moment, he told them all about his plan regarding escaping to capital and leveling up using questionable tactics, and at the end he added:

"So I don't care if I'm not going to see any of your useless asses for the next month, no I might as well not get to see any of you ever again, I don't care anymore, next time I see eris I won't hesitate to be reborn, instead of returning to this atrocious world. I'm going to my room."

Needless to say, the girls weren't happy about his words. He could hear their insults for the solid 10 minutes after he slammed the door to his room.

And that is how he found himself where he was right now.

My plan backfired but how the hell could that bitch Aqua make me feel bad for actually reaching the outcome that I wanted in the first place. He should be on his way to the capital right now but he couldn't find the motivation to get out of bed. Being called shit-Neet, even if somewhat justified, was becoming annoying. Even if he wanted to change, what could he possibly do?
This whole thing was meant to be just like in those isekai anime he watched. Being transported to another world as a chosen hero destined to kill the main villain and save everyone, having a harem of cute girls fight for his affection, that was a life he expected. Not this fuckery that he was given. Having no broken abilities, not being gifted in any way, having troublesome idiots as his party members and most of all dying several times already.
To give insult to injury, after becoming somewhat capable in terms of strength, he had to reset back to the square one. With that thought he looked at the corner of the room where few bottles of this cursed potions still stood.

"Moi sees that in the future you will be willing to pay enormous price to get every last bottle of this elixir, as it will open a new path for you, Kazuma satou."

New path my ass. I bought those potions because they were cheap and because for what I knew Vanir's prophecies were always right. I thought that I could find some use for it, but as it didn't work on anything other than humans and even in this case they had to drink every last drop of the potion for it to had an effect, it was a totally useless garbage.

Kazuma sighted and took out his adventurer's card from his pocket. Earlier he only looked at the corner of his card where a large number "1" regarding his level was. After that he shoved it deep into his trousers, not wanting to see the results of all his blood and sweat gone, but right now he needed to know how much damage has been done.

Let's see, level one indeed, stats don't look all that lower than before but all his precious skill, his only saving grace. Were still there.

"...Huh? WHAT THE FUCK?!"

"Lurk."

It activated normally as it usually did in the past. Kazuma was shocked by a sudden revelation. This potion was meant to revert one who drank it to level one, so it was only logical that it would also remove all acquired skills as well.

Suddenly Kazuma jumped out of his bed, there was one thing that he had to check, if it really works as he thought then… he grabbed one more bottle of the potion and rushed out of his room.

He entered the kitchen and took out something he had hidden a long time ago.
Dragonlizard meat. This was probably one of if not the best food in terms of exp given when consumed. He fought the urge to just eat it raw and cooked it quickly. After consuming the whole thing he looked at his adventurer card again. Level 4 it said in the corner.

Wow it really is easy for the adventurer class to level up. Now how should I do this? Thanks to hanging out with a lot of different people I have a lot of skill that I could level up, well for the sake of science let's start with this. Kazuma spent two available skill points on "treasure detection". Leaving one point left undistributed he drank a potion that he brought with him. Again his level was reduced to one but his new skill was unaffected.

"Treasure detection."

It seeed to be working fine. Kazuma took out an empty glass from the cupboard.

"Create water."

A small stream of water started filling the glass.

"Ok so my old skills are still fine, but there seems to be a catch" He said as he again looked at his adventurer's card.
"Seems like the skill point I left unused disappeared." He tried spending points on anything else, to see whether it really vanished or just wasn't showing on the card but nothing happened.

"This can prove to be a little tricky in the future, but for now it's just a minor inconvenience."

So the way it works is that it resets the one who drank it back to level one and lowers one's stats to their basic level. But then for some reason it leaves any learned skills and spells unaffected while also removing any unused skill points that were obtained earlier.

Usually in MMOs things that let you reset your character either give you a clear start meaning they remove anything that you learned or they let you redistribute your skill points by giving you backthe ammount you spend learning stuff. Kazuma wished it would work like the latter because it would make it easier to abuse but his plan could still work with what he was given.

Right, his plan.
The moment he saw his skills unaffected by a potion he already knew how to exploit it. The way this world leveling system worked, was that the ammount of exp required to level up increases with the level of the individual, being very small at the start, and rising significantly with time. Adventurer class had a significant boost to earned experience which meant one thing.
If he kept on getting exp and resetting using the potion, he could, in theory, get unlimited skill points.
But still, this was just a theory. He already had experience with becoming insanely powerful by exploiting a bugged game mechanics, but this was a real life we are talking about right now. Also is it really what he wants to do? Does he have it in him to finally be serious about something?

Lost in a train of thoughts he didn't even notice as he wandered back upstairs and back into his room. He lied on the bed, still unsure that to do.

Then somebody knocked on his door.

"Kazuma." It was megumin

"Oh Megumin, do you need anything?"

"I'm going out to cast my Explosion" She said without opening the door.

"Oh right, wait a second I need to change my clot..."

"I'm taking Aqua with me, I just wanted to inform you that you will be alone in the house for the rest of the day."

"Oh… I see. Then I'll wait for when you come to sleep with me. Actually there is something I want to talk with you about."

"I don't think I'll be coming today Kazuma. You can go and sleep with your perfect little sister in the capital for all I care."

"L-listen Megumin it's really important…" He stopped talking when he heard quick footsteps on the stairs. He went and opened the door. Megumin wasn't there. It seemed she run off as fast as she finished talking.

Well it was to be expected, Megumin is probably still angry for what happened earlier. But then why do I feel so shitty right now? I can't deny that I grew fond of our explosion trips and sleeping together became my favorite part of the day, so after not getting to do those things for a while I wanted to experience them as fast as possible.

No, that is not all there is to it, after all that happened today, I wanted to relax and spend some time with her more than ever.

He wanted to just go and chase after her but at the same time he was mad that she just treated him this way.

"Fuck, that should I do" Kazuma yelled. He was contradicted. Earlier he felt that he was right on his part. But now after he learned of this unexpected effect of the potion he wasn't so sure anymore. Should he change his mind, explain the situation with everybody and start genuinely working toward slaying demon king or should he just run off to the capital without saying anything to others? Both options felt equally tempting.

"Yare yare daze, I guess there is only one way to choose something." He took out a golden coin from his pocket.

"Heads for telling them and tails for running off."

He tossed the coin high into the air but while he looked at the spinning gold piece another thought crossed his mind, and it changed everything. He grabbed the coin before it touched the ground.
There is a reason why people choose a coin toss to decide things. It's not because they want a pure chance to do the job for them. It's because in this few moments of uncertainty you actually realize what you really want to do. And that was the case for Kazuma as well.

I'm not going to work with those 3 but I'm not running away either. I'm going to abuse this potion to become insanely strong in secret until it's time for my grand entrance as the savior of this world.
His plan was simple. He was going to continuously rise his level to a certain point, learn some useful skills and spells and then drink the elixir again, repeating the cycle. He'll just need someone to help him start this off and teach him some offensive abilities so that later he can just farm alone. Well he knew exactly who to ask for help he just need to wait for her to arrive at Axel, which he though would not take too long considering how often she visits to challenge her rival. Yes the plan was perfect all he had to do now was wait until..

Hold on a second, he thought, as he looked at the few bottles of potion remaining in his room.

"This is clearly not enough to get me where I want to be." A second though crossed his mind and he started to shiver.

"Damn it, I need to get to wiz's shop quickly!"

What he remembered was that Vanir indeed said that the time will come when Kazuma would be willing to pay enormous price to get his hands on this potion, but money was not his concern. He grabbed his wallet and dashed through the door. What Vanir is mostly interested in are negative emotions, so there is a chance that he is going to destroy all he has in stock just to fuck with Kazuma and feed off his anger and frustration. He needs to act fast so it won't happen.

I just hope it's not too late already Kazuma thought.

Magumin was standing near the main door of the mansion.

"How much longer are you going to make me wait Kazuma."

Suddenly she heard some heavy footsteps on the stairs and saw Kazuma running towards her. Finally, her plan seemed to work as intended.
She knew, that if she acted a little cold to him, he would finally get his shit together. Still, she expected him to come chase after her right away. What made him wait so long? Well it doesn't matter now.

"Kazuma..."

"Megumin? What... I see, so you were just messing with me again?!"

"Don't yell at me, you would never act on your own initiative, you coward. Now stop acting like a little bitch and..."

"Get the fuck out of my way Megumin."

With those words he pushed her aside and ran out of the mansion.

Magumin was speechless. Did she overdo it earlier? She has never seen him this angry before. But it wasn't all there was to it. The look he had on his face, it's just like if something important was being taken away from him. Was it her fault? Was it because of what she said earlier? And when she remembered his words, that he was not going to come back the next time he dies…

This was when she was no longer able to hold the tears back.