Narumi Fujishima may seem like a normal high school student at first glance, but in reality he is a pessimistic outsider. Due to his father's work, he had to constantly transfer schools, and thus he has never managed to become a part of society. When he is forced to join the gardening club by his cheerful classmate Ayaka Shinozaki, Narumi encounters the genius hacker Alice, who lives in isolation above Hanamaru, the ramen shop where Ayaka works part-time. He then discovers that Alice is running a special private detective agency, and that all her professional associates refer to themselves as NEETs: Not in Education, Employment, or Training. Joining the NEET detective agency due to his personal connection with a criminal case, Narumi finds himself entangled in a world of dangerous investigations conducted by the ill-assorted group of detectives, all the while trying to track down the crime syndicate which seems to have mysterious ties to Alice.

Tooru Kirishima's notoriety is spread far and wide in the underworld. He is most commonly known as The Demon of Sakuragi—a man who is not afraid to resort to violence if deemed necessary. After almost jeopardizing a peace treaty, his boss tasks him with the most difficult job he has ever had: taking care of seven-year-old Yaeka Sakuragi—the boss' precious daughter—so that Tooru understands what it means to be responsible for another life. At first, the two do not seem to meet eye to eye, as Tooru has no clue on how to communicate with Yaeka, and the young girl is not used to expressing her emotions. However, as time goes on, they come to understand each other despite their differences. The fearsome right-hand man of a yakuza boss and the child he must protect are about to learn that family is not always bound by blood.

On their way back from the 18th floor, Hestia, Bell, and the others accidentally uncover a hidden, mystical hot spring, and they decide to stop by to refresh themselves until creatures lurking in the dark appear to attack them.

Third season of One Punch Man.