Dungeons have appeared in modern-day Japan. Shutaro Hanaoka, a middle-aged man with an old-looking face since childhood, is a lowly, unremarkable office worker. But on the morning of his 40th birthday, which he greeted as usual with zero romantic prospects—suddenly, his 「Status」 glitches! And the job he awoke to was the ultra-rare 「Grand Mage」! After passing the selection for the elite monster-hunting unit 「Defense Organization」, he accidentally goes viral during an official livestream. Surrounded by a beautiful captain and cute female colleagues, he begins a new life as humanity's strongest hero—a dream he'd held for years! He couldn't become a 「Mage」 as a 30-year-old virgin, but at 40, he awakened as a 「Grand Mage」!? From 「Let's Become Novelists」, a wildly popular dungeon harem hero tale!