Coiling Dragon - Book 2 - Growing Up - Chapter 1 – Magical Beast, Shadowmouse

The protagonist wakes up to a superpower one day, out of the blue! But there’s no organization targeting the protagonist’s superpower! The prettiest girl in his grade doesn’t turn out to be a psychicer like the protagonist himself! No door opens to another world and he doesn’t get summoned! There is no secret history in the protagonist’s past! There is no reveal explaining the protagonist’s sudden attainment of his superpower! So normal! Such overwhelming normalcy! He graduates from school and gets a job without anything happening! He lives as a mediocre working adult! Having enough power to fight against all of humanity yet not seeing anything happen finally makes him snap! Fine, be that way! If this is the way it’s gonna be, then I’ll make it! I’ll make the secret supernatural organization myself! Welcome to my manmade extraordinariness!

I’ve reincarnated as the reverse harem game’s villainess, the one and only step-daughter of the Eckart duke family.

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates