Saenai Ossan, Jitsu Ha Saikyou

Renji, once the strongest dungeon conqueror in the country, has spent the past ten years forgotten by society and living an unremarkable, slovenly life. His quiet routine changes when Satsuki, the daughter of a former comrade, asks him to teach her how to conquer dungeons. Dungeon streaming has become popular among young people, and high school student Satsuki wants to join in. Renji thinks he can no longer be bothered with dungeons, but he cannot turn her away and goes in with her. Though he seems like an out-of-date middle-aged man, Renji is still the strongest, and his return makes waves in the dungeon-streaming world.