Warning: Before dropping the story due to not making Lucifer strong in this chapter, read through the entire chapter first. By the time he goes off to Soul Society he can fight against most of the regular Captains.
After Lucifer pierced through Ichigo's heart, he suddenly woke up in a familiar underground training ground being face-to-fate with Kisuke Urahara asking him a question.
As his thoughts and those of Ichigo completely merged together, he felt a change also happen to his personality and general thought process. Unaware, he also gained a frown on his face, unlike that of the original Lucifer, similar to the original Ichigo Kurosaki, which has became an almost instinctual action for that personality.
Kisuke Urahara eagerly waited for an answer from him, until he finally replied "Would you let me re-enter my physical body, Kisuke. I will then answer all your questions.", with his Japanese being more natural sounding after his personality had fused with that of Ichigo, but still retaining a slight British accent to it, due to his father creating him that way, meaning that it is natural and part of the ability called [Language] that all angels and devils possess when they are born or are created, with his biological son Rizevim Livan Lucifer also having inherited it as part of his own magic.
"Very well." replies Kisuke, agreeing to it, as it would mean he would be a much smaller threat in his eyes should he happen to be an enemy, due to being in a physical body.
The reason Lucifer did that, was that when he tried to first use magic in order to teleport to his body the moment he woke up, he was unable to do so, as souls use a different form of magic. He does not know any soul reaper magic and even if he knows it, he is unsure that he could actually use it. He may currently be similar to a normal plus, which is a regular soul without powers, despite him still having his demonic energy reserves. He also could feel that his demonic energy reserves are slowly starting to leave from his soul and there might be a chance that he could either disappear due to originally not being from this world or he could becomes a regular plus as the time progresses. He has always been smart, so he chose the most logical solution, knowing that now he also has to truthfully explain to Kisuke Urahara what has happened to him in the shattered shaft as Kisuke appears to be a smart person based on his personal observations on him, despite his seemingly eccentric personality, meaning there is a slight chance he could see through his lies despite him being a master liar, as merging his personality with the original Ichigo his thought process has greatly changed, with him now wishing to truly save Rukia due to his own pride for having been saved by her in the past, while also comparing Rukia's punishment with his father's despite them being different.
Lucifer walked over to what would become his physical body that was lying on the ground, and re-enters it the normal way that Ichigo did.
The moment he does that, he could feel his demonic energy trying to adapt to this human body, while his body feels like it is burning up, but it does not hurt him at all. If he has to guess, his body is trying to slowly adapt to his soul form, meaning over time his body will turn to that of a Pure-Blooded Devil and the original Lucifer.
Now as he is standing up, while being in the original body of Ichigo Kurosaki, he decides to tell Kisuke what happened while being in the shattered shaft, watching Kisuke's eyes and facial features for his reaction.
After finishing telling the story to him, he sees Kisuke take out a phone from his pocket.
"Isshin," says Kisuke over the phone "We have encountered a serious problem trying to restore Ichigo's soul reaper powers.", sounding serious "Come over to the training ground as fast you can as this could not be told over the phone. I also suggest you close your clinic for today."
Kisuke then puts the phone away and tells Lucifer "Your father will be over in a few minutes. And by this I mean the father of Ichigo Kurosaki, as I do not know if you even consider him as your own father.", while then continuing "Before he arrives, tell me what you wish to do from now on."
"I don't know." replies Lucifer, knowing that he is now in a new world, while considering the potential threat levels of both hollows and soul reapers, having not seen their peak or their quantity "If possible I wish to someday return to my original world. I feel that my current body would eventually change to my original body over time and that of a Devil. But after merging with the personality of Ichigo Kurosaki, I wish to truly save Rukia Kuchiki, call it as not wishing to be in her dept due to her once saving my life."
"But could you save her in your present state?" asks Kisuke, stating the facts "After all, you said that your body is changing to that of a devil, meaning you are currently close to that of a human or even a human. Could you even use your full powers?"
Lucifer tries to use his powers, now that he is in a physical body and manages to summon a small and unstable spear of black-colored light. This ability is called Demonic Brilliance of Evil Light, and is only inherited by some of his bloodline, it is similar to the light used by angels and fallen angels, only that this light could injure both holy and demonic beings, being a light that is unholy, while the user himself is immune to their own ability. While doing so, his hand gets slightly burned in the process due to his body.
"Pathetic." replies Lucifer, laughing at himself "At my current state I do not even have the strength of a Mid-Class Devil. If others could see me now, I would probably never live though this humiliation."
"I see," hums Kisuke, seeing their starting point despite not knowing about the devil power levels, but assumes that Mid-Class is at the lower end of the ranking system "I honestly don't know how to train you. Do you have any other abilities or any notable talents in any martial arts or swordsmanship. How does your devil magic work, as I assume that it is completely different from regular kido used by soul reapers. Also, would you recover your original energy reserves once your transformation into a devil is complete?"
"At the time I died, martial arts was at a fairly basic level." replies Lucifer "The karate I learned as Ichigo Kurosaki is more useful than most martial arts of my time. The only weapons I used while alive where light spears. As for magic, I will most likely recover my full demonic energy reserves and physical strength once the transformation is finally complete, devil magic works on imagination and does not have any limits as long it is still devil magic, it only depends on the talent of it's user which I have, their magic energy reserves, and knowledge on how the spells work."
"That's good then," says Kisuke "I should then change my original plan, by having you train under both Yoruichi and Tessai instead of me, while I will go out and train the friends of the original Ichigo Kurosaki instead of Yoruichi as I originally planned, as it would be more reasonable for you to have learn martial arts and recreate shunpo and kido from the masters in their respective fields."
They then both see that Isshin Kurosaki has arrived at the training ground, making them stop their conversation.
"Kisuke, Ichigo?" asks Isshin, having a confused facial expression after seeing both of them be alright, not knowing the reason why Kisuke called him.
Lucifer decides to reveal the reason to him "I am no longer your son, Isshin Kurosaki..."
Before Lucifer could finish, he is stopped by Isshin shouting "What! I know that I am not the best father, but I still try my best. Do you now consider Kisuke to be a much better father than me?"
Lucifer sighs at the misunderstanding and tells Isshin "You did not let me finish, father.", while feeling weird for calling him father as he still has painful memories of a different father "What I mean to say to you is that I am not completely Ichigo, I am also Lucifer."
"Kisuke!" shouts Isshin "Could you please explain to me what Ichigo is saying?", thinking Ichigo is now insane for calling himself Lucifer.
Kisuke sighs and explains everything.
By the time Kisuke is finished, Isshin has tears in his eyes and asks "What happens now?"
"I don't hate you at all, Isshin." replies Lucifer "As I am also Ichigo at the same time. In my mind I see you as a much better father than my original father in heaven."
"Then if you are also Ichigo at the same time, how about you stay as my son."
"That would be difficult, as someday I will no longer look anything like Ichigo and my personality is different from the original Ichigo Kurosaki."
"I see." was the sad response of Isshin "What am I going to tell to your sisters?"
"If I may," interrupts Kisuke "I already have thought of a plan for this problem, as Lucifer still has retained Ichigo's original appearance."
Lucifer, Isshin and Kisuke arrive at the house of the Kurosaki family.
"We're home." announces Isshin.
"Welcome home", greets Yuzu, smiling, as Karin is watching TV and not reacting to their arrival.
"Karin, Yuzu." says Isshin, gaining both of their attention due to his serious tone "Ichigo has something to say to both of you."
"What is it Ichigo?" asks Karin, being interested whether Ichigo has got himself a girlfriend and who the man with a green bucket hat is.
"The truth is that a friend of Kisuke Urahara here has offered me a scholarship for a top high school in Japan with a guaranteed chance to enter Tokyo University after my graduation with all his living expenses paid, but with a reasonable budget, due to my good grades and athletic ability.", lies Lucifer, with neither of his sisters suspecting anything "So, now I am moving out of this house and going to live alone in Tokyo."
"No!" shouts Yuzu and runs to her room, while Karin is in shock from the revelation of her brother leaving.
"When?" asks Karin with a shaky and quiet voice.
"Tomorrow." replies Lucifer, knowing the changes to his body would not be noticeable after only a single day, as his demonic energy is still trying to adapt, and he can that way say goodbye to Ichigo's sisters and ease the worries of Isshin, while then walking to Ichigo's room in order to pack some stuff as he should show them he is leaving for Tokyo.
The plan that Kisuke Urahara had was that Ichigo would die sometime while he is in Tokyo, having two mod souls put on an act worthy of William Shakespeare who both Lucifer and the original Ichigo greatly respect. One mod soul would drive a speeding car and hit him, while the other would be inside a specially made gigai of him and die. With Kisuke having already made the gigai before coming here based on the Lucifer's current body.
The time before his departure, Karin and Yuzu did not notice anything unusual about him as Lucifer was a master actor and liar, having the original Ichigo's memories.
Lucifer waves his hand to his family in order to say goodbye to them, as he enters a car driven by Tessai Tsukabishi, who would then take him away from Karakura town to Tokyo, while in actuality they would take him to the the underground training ground in the Urahara shop.
"Your a great actor Lucifer.", says a black cat that sits on the back seat of the car.
Lucifer turns his head around and says to the cat "You must be Yoruichi Shihōin."
"Indeed I am." replies the cat, being curious about his reaction "Your not surprised by my current form."
"Not really." replies Lucifer "I have seen both nekomata and even a few devils transform into cats."
"Interesting." thinks Yoruichi "Maybe this could also be something that I would be teaching you, if you are interested that is."
Tessai starts the car and they all drive away, while Isshin is hugging a crying Yuzu, as he himself is holding back his own tears in order to not reveal the truth to his daughters.
Lucifer has more than a week for training and adapt to this body, before leaving off to Soul Society.
Authors Notes:
Although I don't like Rias Gremory, she is still the sister of the current Lucifer, meaning a potential person for a political marriage.
About Lucifer's accent, I have read from somewhere that Rizevim speaks in an English accent, so I decided to make Lucifer unique that way.
In this fanfiction I made it so that devil magic needs both spiritual and physical energy to be used, slightly similar but different to Chakra in Naruto. Also as no Arrancar in the series has used Kido, Lucifer in soul form can also not use kido, as I am certain Aizen has tested whether his Arrancar could use Kido.
I read somewhere that Sirzechs Lucifer was said to first meet Souji Okita in the form of a black cat.