Toradora! - Volume 10, Chapter 5

Struck down amid the battle, the Hero and Demon King meet their demise. As their souls linger on the edge of the afterlife, a mysterious force intervenes, merging their fragmented souls together with a new being. Rusty, the living armor, now affected by their memories and presence, embarks on his own quest. Will he seek revenge on those who betrayed the hero, or will he fulfill the desires of the fallen demon king? or instead, forge his own path?

During a party one evening in the royal palace, Rachel, the eldest daughter of Duke Ferguson, was reproached by Prince Elliot for sins she didn’t remember committing and their engagement was abandoned. Rachel informed everyone she had not committed the acts they were accusing her of, but she was dragged away out of the party venue and thrown into the palace dungeon.

Upon meeting the girl who would become her adopted younger sister, the duke’s daughter Christina regained memories of her previous life. Through those memories, she learned that her new sister, Mishuli, was the heroine of a certain story. And though the story depicted a Christina who abused her sister, the real Christina turned into a siscon who spoiled Mishuli to no end.

Three years ago, the animals and plants on Earth underwent crazy and unexplainable changes that included transformations, reversions, and the addition of otherworldly species. And it was the start of a brand-new type of profession in the new generation of humanity – Monster Trainers, people who specialized in taming monsters.

On his 18th birthday, the protagonist of the story, Gao Peng, suddenly received the ability of being able to see the attribute data frame of monsters. With his ability, he aspired to become the strongest monster trainer that ever lived while looking for a method to revive his parents!

- Description from Novelupdates