Yu-yu is a young man from Kanazawa, Kaga Province. He is 15 years old and is currently in his third year of junior high school. He can sense other people's emotions, but he is troubled by the fact that he cannot say no when asked. Yu-yu couldn't bear going along with his sister's hobby any longer, so he ran away from home. Megumi Okura is the one who saves him. Megumi invites Yu-yu to "Wonder Hill," a nighttime amusement park where her friends hang out. Yu-yu meets Megumi, Zakusa Ishikame, and Tomari Seto, members of "Team Blackout," a group that meets every night to play Vanguard.