Nanbu Shouhei lives and attends a high school in Tokyo but in his childhood, he briefly attended kindergarten in Kyoto while living with his mother and maternal side of the family there. He started playing an online fantasy RPG called Fang of Ouroboros three years ago and met a player who rescued him when he was a newbie. The other player claimed to be Senke Tomonari, who had been one of his kindergarten classmates in Kyoto. They became close buddies through the game though they never met or talked over the phone but only communicated online because of the distance. When Nanbu's high school organized a study trip to Kyoto, Nanbu and Senke made a pact to meet up in the flesh since they have not met since their kindergarten days. Nanbu duly appears at the meeting-place arranged by clues from the online game but Senke does not turn up. Instead he keeps getting puzzling mails from Senke and he is assaulted by a bow-gun when touring Kyoto. Is the "Senke" Nanbu met online really Nanbu's childhood classmate or an impostor? Who is behind these assaults?