Yu-yu Kondo is a third-year middle school student who resides in Kanazawa, in the country of Kaga. Yu-yu frequently becomes engrossed in his sister’s pastimes since he is unable to refuse requests. Megumi Okura saved Yu-yu when he was about to give up and fled his house. Megumi extends an invitation to Yu-yu to join her pals at the “Wonder Hill” nighttime amusement park. A large number of young members of the Vanguard-focused group “Team Blackout” congregate at the theme park. And that is how Yu-yu first meets Vanguard. He is captivated by Vanguard’s charm as well as the new friends and world he has never seen.