Mushoku Kakutou: Neet Combat

Kurosu Kengo, a man who ran away from society after being bullied, spends his days commuting between his home and the arcade. His only purpose in life is fighting games. Kengo is abnormally devoted to fighting games, and one day he realizes that he can now replicate the movements of game characters. However, a former bully interferes with Kengo's life... This is an exciting, life-changing action story about an unemployed man who somehow becomes the strongest fighter!

(Source: YanMaga Web, translated)