MTL - Game Designers: You Don’t Understand Charity - Chapter 8 Brother's game can't be trivial

A man is reborn into the world of Avatar: The Last Air Bender as a waterbender from Katara's tribe. Best of all, he was the same age as her, and he had a system with him to help.He knows the future and a system that lets him continuously get stronger by completing quests or long-term missions, as well as giving him the ability to copy abilities from others for himself. He will become invincible in the world of Avatar, even more so than the Avatar himself.

Inside the 3000m underwater station, an international group of scientists and engineers live and research for possible settlement of entire human race. Park Mu-hyun, a reserved dentist joins the station in hopes for a quaint life in the deep sea. However, things quickly go south when the station gets attacked by a mysterious group of people.As the water starts to fill in the living quarters, Park Mu-hyun grabs his backpack and immediately runs for his life, but where to? Now, the peaceful station becomes the ultimate survival stage of cult madness and chaos.

Entering Tokyo in the bubble era, in this strange era, the only familiar ones are Matsuda Seiko, Nakamori Akina, Kudo Shizuka…

- Description from novelbuddy

On the Great Land of China, forces clashed for the sake of supremacy and Bloodline Warriors ran amok; the conflict of the strong threatened to shatter heaven and earth. A young man named Lu Li—nothing more than a humble Coffin Carrier from the Northern Desert—came along with Lu Ling, his sister. The two were regarded as puny insects and bullied, but little did people know that Lu Li had the strongest Bloodline of them all in him.