Immortality Martial Arts: I Started with the Five Animals Health Fist - Chapter 9 - 7 Internal Refinement of Organs! Stamina Like a Horse!_1

At age 5, Amon unlocks the unique «Fury» genetics and is what caused his behavior to change.

After living with his grandparents for 11 years he learned to behave. For reasons he can’t know, his grandparents faked their deaths, and now he needed to move.

Now he would have to face a new challenge which was to live with his mother and stepfather and two twin sisters not linked by blood and go to school.

A novel revolving around being transported to another world with an op system. The mc spends his day chasing skirts and doing missions to level up. A standard journey to the top with lots of girls from various animes and games with a twist of that gaming feel (hunting mobs, doing missions).

- Description from novelupdates