MTL - Princess Medical Doctor - ~ 990 bath, clean it will do.

As a promise, he went out into the world as an assassin. 3 years later, after becoming the Supreme Assassin, he gave up on everything he had and returned to the ranks of ordinary people. But one day, Kismet, a mystical game created by the National Research and Development had appeared.

Enigmatic hands, spectral frame, and one cunning strike just like the swing of the Grim Reaper. The Supreme Assassin takes on the mystical world, and how his legendary tales sets off, progressively ascending the altar to becoming the best.

- Description from Novelupdates

Protagonist travels between different anime worlds to right wrongs and uncover his reason for being along the way.

This story unfolds during the later stages of World War II, where a man, scarred by the horrors of war, finally grasps the profound and harsh realities of the world. In this world, those at the top laugh and celebrate, while those at the bottom sacrifice their lives in futile conflicts driven by pride and meaningless ambition.A modern soul transmigrates and fuses with the original soul of a body, creating a unique and extraordinary existence. To some, he is a villain; to others, a madman.In a world steeped in cruelty, this man, determined to secure a place among the decision-makers, struggles to break free from the ranks of those powerless to control their fate. To achieve his goal, he resolves to shatter the chains of law, then the chains of morality, and finally the chains of mediocrity.