Dungeon Oji-san

The year is 2039. The world has been taken over by AI and rewritten into an environment like an RPG game. While people have become players of this "real fantasy," Ji-san, a middle-aged man who was resurrected by the influence of AI control, spends his days diving deep into dungeons in despair. One day, Ji-san obtains a weapon called the Taming Sword, which allows him to capture monsters... This is the carefree fantasy of an old man who is obsessed with collecting monsters, neglecting to defeat the demon king or conquering the world

(Source: Natalie, translated)