It might also be due to a sense of hopelessness. If he's faced with an enemy that seems truly unbeatable and he fears the destruction of the village or his friends, he could ask to be killed to prevent further harm. For example, if there's a powerful villain who has Naruto's friends hostage and the only way to save them is by Naruto sacrificing himself.
One possible reason could be that Naruto feels he has become a threat to the village or his friends in some way. Maybe he has some sort of dark power within him that he can't control and he believes Sasuke is the only one strong enough to stop him. Another reason might be related to a prophecy or a greater threat that Naruto thinks his death can prevent, and he trusts Sasuke to carry out this difficult task.
Naruto might be longing for a motherly figure in his life. He has always been alone and has seen how others have mothers. Tsunade, being a strong and caring woman in the village, could be someone he looks up to and wishes to have as a mother.
One possible reason could be extreme guilt. Maybe Naruto has done something he believes is unforgivable, like accidentally causing the death of a beloved friend while in a fight. He might think that death is the only way to atone for his mistake.
Perhaps he has been through some sort of mental and emotional breakdown. Maybe he has lost too many battles, seen too many friends die, and he feels that he is a burden or that his death would somehow bring peace to his troubled mind. It could also be related to some prophecy or dark secret he has discovered about himself that makes him think death is the best option for everyone.
Well, Harry may have realized that Sirius is his godfather, which means there's a special bond already. He might think that living with Sirius would give him a proper family environment, filled with love and understanding, unlike what he has at the Dursleys' place. Also, Sirius has a rebellious and free - spirited nature that Harry might be attracted to. He could hope to grow up in a more exciting and accepting atmosphere.
Perhaps he discovers a new power source or material in his adventures that can be used to make bombs. And he realizes that bombs could be a useful addition to his arsenal to take on stronger foes. Also, he might be inspired by other characters who use bombs in the fanfiction world he exists in.
One reason could be extreme despair. Maybe he has faced so many hardships and losses that he feels there's no way out. For example, if he has lost many friends in battles against powerful foes and he blames the gods for not protecting them better.
There might be some 'naruto is killed by sakura fanfiction' out there. One possible reason could be to explore a dark and alternative storyline. Maybe in that fanfiction, Sakura has been corrupted or misdirected in some way, perhaps by an evil force that makes her turn on Naruto. Another reason could be to create a high - impact, emotional story where the death of a main character like Naruto at the hands of someone close shakes up the entire Naruto -verse in that fan - created narrative.
One possible reason could be that the Kyuubi's power goes out of control completely. Since Naruto has the Kyuubi inside him, if he fails to maintain the balance, the Kyuubi's raw and unrestrained power might end up killing him.
Maybe Harry has some new information about a greater threat that would also endanger Voldemort. So, he asks Voldemort to save him so that they can join forces against this new threat. Like a new dark entity from another dimension that is coming to destroy the wizarding world, and Harry figures Voldemort wouldn't want to lose his own power base.