Toaru Majutsu no Index - Volume 12, Chapter 2: What kind of penalty game? Pair_Contract.

The protagonist, a renowned gamer/YouTuber aka [TorchDancer] is a master of the game “Tril Trilo Trilogy.” When offered a chance to playtest the prequel, “Part 0,” he jumps at the opportunity. But a twist of fate plunges him into the game itself, transforming him into the series’ ultimate villain, Frank Wonderstein. Trapped in a monstrous body, he must navigate a dangerous world, unraveling the secrets of the game and his own destiny. Can a hero become a villain? Or can a villain find redemption? Well, you’ll just have to read to find out.

After transcending to a new world, Ye Xuan miraculously obtained the Swallowing System.

Tenjou Yuuya has been a bullied boy since the past.He lives in the home of his beloved grandfather while he goes to school. As usual, he receives a harsh bullying, and he takes an extended absence from school to have some time to heal his wounds.While on this long time of absence, he takes the opportunity to clean his grandfather’s house and goes to a room he never went before, where his grandfather keep many different objects that he gathered from his travels around the world. While he was arranging the objects, he found a door not on a wall among the objects.Out of curiosity he opens this door, what he found on the other side was…

One day, Zhang Fan, a poor medical student, receives a medical system from the future. This turns him into a new shining star in the medical field. Along the way, he must face medical corruption, competition, and infighting from other doctors, and even find time for a love life as he strives for the top of the medical field!