15-year-old Ninako Kinoshita has never been in love until an encounter on the train with her school's most popular boy, the quiet Ren Ichinose. As she grows closer to Ren, she falls in love with him, but must learn to cope with the unfortunate fact that Ren already has a longtime girlfriend.

Brother and sister are drawn into a thrilling game of survival, in which they use a bizarre device called SCM to turn others into their slaves.