Ichiro Shibazaki is an unassuming 45-year-old middle-aged man who works a grueling, low-paying job as a dungeon cleaner. During a typical shift, he discovers a young girl under attack by a monster and effortlessly slays the formidable beast using only his trusty deck brush. He quietly departs without leaving his name, completely unaware that the girl is actually an immensely popular live streamer. His incredible feat is broadcast live to millions, sparking massive online frenzy over the unidentified god-like middle-aged warrior. Major guilds, S-rank explorers, and high-profile figures frantically launch searches to uncover his true identity, all while the completely oblivious cleaner goes about his daily routine.