One Piece: I am Imu - Chapter 13: Doflamingo’s help!

Chu Li was a particle physicist until a freak accident took his life and transmigrated him to a parallel universe – one where he wakes up with inexplicable abilities and finds himself in the running for a job in the imperial palace.

Reborn and returning, he possesses medical skills, can practice immortality, has a slave who is the king of killers, and a maid who is the school beauty pursued by everyone. Even casually taking out a piece of trash can shock the world. His return has set this world ablaze.

One of the few self-cultivator who exist in this modern world; due to an unfortunate event, completely destroyed his body in an explosion. Using all his effort to save his primordial spirit, he ended up in an strange magical world and had to start all over again. From a fallen aristocrat to the Warlord of Chaos, this can no longer be summarise as legendary; this is the life of the God of War.

- Description from Novelupdates