DxD: Scion of Lucifuge - Chapter 266: P.E. class—Wizard of the Four Fists Misaki Sasasaki—

Is a flower demon with three hundred years of cultivation.

Shao Zi’s biggest wish is to beat up that egghead Scholar (shu sheng) that always comes to water plants at noon.

But when she got close and rubs her hands in preparation for action, she realizes that she’s clearly playing along to someone’s rhythm ah!

- Description from Novelupdates

16 years old-- most boys would be falling in love, as their hormones all rise to unprecedented levels. Most boys at Riley's age would have dreams; dreams that will slowly grow into passion. Riley, however, at age 16... killed the world's number 1 superhero.

One day, Luo Jian woke up from his sleep and found himself in a locked chamber where the door and window were all sealed. A note with a few lines written on it was tacked to the wall: “Escape from this room within an hour, otherwise, you will die.”

There is a sequel called Reincarnation Night (轮回之夜) that takes place in the same universe but has different main characters

- Description from Novelupdates

Blessed with unlimited mana, Noah travels the worlds and sees rampant corruption and injustice.