MTL - I, Doomsday, Have Been In the Core of the Sun For a Hundred Thousand Years - Chapter 336

A mecha otaku is reincarnated into another world as Ernesti Echevalier (Eru). In this world there exist huge humanoid weapons known as Silhouette Knight. Dreaming of piloting those robots, Eru, with childhood friends, Archid Walter and Adeltrud Walter: together they will aim to become a Knight Runner, pilot of Silhoutte Knight.

He died on the wedding of the girl he had a crush on, after a long and successful career. After convincing Yama to send him back to the world, he decides to fix the areas in which his life went wrong. Realizing the lack of love and romance in his past life, he sets out to conquer the hearts of various women.

- Description from Novelupdates

The person whom the world revolves around.

Can you get used to dying? Not really.

When a particular universe was born, its seven primordial Concepts acquired an ego. Omniscient and omnipotent, they seek since to enrich their home. To do so, they plunder other universes, capture young civilizations and plagiarize ideas. Many monsters, gods, civilizations, and races are competing for the eighth throne.

Eons later, it is Earth's turn to be torn away from its Sun.

Humanity begins its integration by participating in a Tutorial. Priam has the luck and the misfortune to finish the Tutorial first. Luck because his reward is a form of pseudo-immortality. Misfortune, because as the champion of his civilization, he is transported to Elysium, the most dangerous world created by the Concepts. Nine out of ten champions lose their lives there on their first day. Fortunately for Priam, he has many lives.