Unosero

"From a young age, I never got along with my fiancée, who has the exact opposite personality, and we don't get along as adults either..." Keith, the head of the court mages, and Miitia, captain of the knights' order, are engaged because of their parents, but they don't get along at all.

To conquer the dungeons that suddenly appeared on Earth a hundred years ago, students now attend academies to train as adventurers. Among them are two rivals: the academy’s strongest delinquent, Sainokami Kuroto, and the elite noble honor student, Mononobe Yukihime. One day, the two of them find themselves trapped in a dungeon… inside a room that they can’t escape unless they hold hands!? Will these sworn rivals be able to clear this high-difficulty mission and conquer the dungeon—!?

The viscount's daughter, Chloe, was the chief magical tools artisan for a country that perished a thousand years ago in her previous life. On the country's orders, she had created many weapons of slaughter. She laments her previous life and decides to, "live a respectable life this time." One day, at her graduation party, her best friend's engagement is broken off because of a lie. Chloe tries to save her best friend by unraveling the truth.