It could be that he's framed for something he didn't do and faking his death is the only way to clear his name. Or perhaps he's involved in some top-secret intelligence work and needs to disappear to prevent exposing crucial information.
Love could also be a factor. Perhaps the character fakes their death to test the loyalty of their lover. Or, they might be in a situation where their love is forbidden, and faking death allows them to start a new life with their beloved without interference. In Chinese novels, love often plays a complex role in the plot, and faking death can be a dramatic way to deal with relationship issues.
One reason might be the author's loss of interest or inspiration. If the writer no longer feels passionate about the story, it can lead to its abrupt end. Another factor could be external pressures like deadlines that force the author to end it prematurely. Also, unforeseen life events of the author, such as serious illness or family issues, may disrupt the writing process and cause the 'sudden death' of the novel.
Maybe he had some secret motives or was under some kind of threat. It's hard to say for sure without knowing more details of the story.
Perhaps he has lost interest in the relationship himself and doesn't care anymore.
Perhaps it has to do with a new and mysterious disease. In fanfiction, new and unique diseases can be created. This disease could be something that attacks his unique chakra system, which is different from others. Since his body is so reliant on chakra, if the disease disrupts it enough, it could lead to his death.
Perhaps he feels guilty about something he has done in the relationship, like having an affair himself, and he thinks by allowing her to cheat, it will make up for his wrongdoings in some way. Another reason could be that he has some kind of self - esteem issue and believes that his wife is too good for him, so he gives her the 'permission' to seek someone else.
It could be that he made the request impulsively without considering the long - term consequences. Afterward, he might have realized that it has a negative impact on their family unit, especially if they have children. Also, he may start to feel insecure about his own self - worth. If his wife engages with another man, he might start to question his own adequacy as a husband, which leads to regret.
One possible reason could be that the husband misinterprets his wife's needs. Maybe he thinks she is bored in the relationship and wrongly assumes that introducing a third person would solve the problem.
This is a very inappropriate and unethical behavior. There could be no valid or justifiable reasons for such an act. It shows a lack of respect and trust in the relationship.
One possible reason could be his inability to handle the stress of having a sick wife. He might be looking for an escape from the difficult situation at home. Another reason could be his own lack of moral values.