I Shall Be Everlasting In the World of Immortals - Chapter 105: Breakthrough at Eighty

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

You take up a student career.

Student career upgrade to lv.7

Acquired skills: primary school knowledge, junior high school knowledge, high school knowledge.

You take the college entrance examination,

You got a perfect score.

Your basic occupation has been upgraded to lv.9, and the job transfer system has been activated.

You change jobs to become a scientist, you gain R&D skills

You use research and development skills to get space fortress construction technology

You use R&D skills to gain starship technology.

You are invincible.

- Description from novelbuddy

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

“How long has it been?”10,000,000 Years, a period of time which he dwelled in the endless abyss as a captive of war.After his fall, he lost everything to the hands of those who stand above the heavens.The twelve gods of the constellations, the Primal Zodiacs!Creatures who descended down from the absolute light to consume all.He fought against them only to fall prey to their destruction, locked away in the endless Abyss.Astroth Vermont lost it all, his will, his empire, his powers and his mind, all he knew was despair.But that’s until he woke up, Returning back to the world as someone else.The Blackest Evil was reincarnated as the Tenth Young Master of the Reinhart Family.His return is going to shape the world, returning all into chaos!Will he exact his revenge?Who knows, welcome to the land of carnage