Arena - Chapter 71 – Gunsmith (Part 2)

In the vast Marvel universe, where superpower was still slowly growing in its infancy, several peerless superheroes tried to find their path in The Marvel Universe. A young adult named Ron from modern Earth unwittingly stumbles into such a world and begins his journey with an unknown power. This is a magnificent yet unknown true marvel world! This is the story of a normal young adult and his adventures!

- Description from Novelupdates

The 27-year-old Wei Han is a slightly fat, slightly chicken-livered, and slightly foolish, pure-hearted and besotted top, and his sweetheart who had been together with him for seven years, in the end, was stolen away by Qi ZhiFan one morning.
Deeply broken-hearted and in despair, he went overboard with binge eating, and ended up pathetically choking to death…

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.

I finally managed to kill the demon lord.