Maybe the father turns out to have been misled in the past life and his actions were not as malicious as they seemed.
One possible plot twist could be that the father in the past life was actually trying to protect the protagonist in a very strange and misunderstood way. He might have made sacrifices that were misinterpreted as enmity. Another twist could be that the past - life enmity was a result of a prophecy that they both were trying to avoid, but in their attempts, they ended up acting as enemies. And in the present, when they start to figure this out, they have to deal with the consequences of their past actions and the new understanding of their relationship.
Perhaps in the end, it's revealed that the whole 'enemy' thing was a misunderstanding caused by some external force in the past life. Like, there was a powerful entity that manipulated their relationship to create enmity between them. And as the story unfolds in the present, they start to discover the truth and gradually reconcile. Also, it could be that the main character discovers that they themselves had some actions in the past life that contributed to the father - as - enemy situation.
I'm not sure specifically which novels are exactly similar to this one. However, you could try looking into novels that involve family secrets and past - life themes in general. For example, some historical family saga novels might touch on such complex family relationships and past - life mysteries.
Honestly, your past life story could be anything. Maybe you were a simple farmer, or a noble person. But it's all in the realm of fantasy and conjecture.
Love and loss could be themes. There might be relationships that are affected by the twists in the character's life. They could lose someone they love or find new love in unexpected ways. Also, the theme of fate or destiny could be present. The twists could be seen as events that are meant to happen, guiding the character's life in a certain direction.
One possible reason could be extreme debt. If a man owes his enemy a large sum of money and has no other way to pay, in some very strange and unethical stories, he might consider giving his wife as a form of repayment. However, this is completely unacceptable in modern moral and ethical standards.
Perhaps the person who was thought to be the father was actually protecting Seto from his real father who is a dangerous or evil figure. Or it could be that Seto's mother was involved in some kind of secret pact that led to this situation, and as the story unfolds, more secrets about her come to light.
Perhaps the plot could be that the father has a secret that he only wants to face in the dark. So he sits there every night, thinking about it.
Well, one exciting plot twist could be that the main character, who is an average gamer in real life, suddenly discovers they have the power to enter the game world. Just like in some classic gamer - related stories. This would completely change their perception of reality and open up a whole new set of adventures. They could meet characters from the games they love and have to fight alongside or against them.
One possible theme is forgiveness. They have to forgive each other for past wrongs as they are now married. Another could be transformation, as they will transform from enemies to lovers or at least to people who can coexist peacefully.
I'm not sure specifically as I haven't read this novel in detail. But generally, in novels with such a title, it might involve two characters who are initially enemies due to various reasons like family feuds, different loyalties, or competing interests. Then, through a series of events, they might find themselves fated to be together in some way, perhaps falling in love or having to cooperate despite their enmity.
One possible plot twist could be that the daughter discovers a long - hidden secret about her biological parents that changes her relationship with her adopted father. Maybe she finds out that her mother was forced to give her up and her husband knew more about it than he let on.