Sayo is a high school freshman. She and Nao are neighbors and childhood friends. Nao is a year older than her, and they have been together forever. They ride the train to school every day. Nao is a very caring friend and treats Sayo as his little sister; however, Sayo is in love with him, but is afraid of confessing because he might turn cold towards her.

Also contains oneshot Cosmic Wonder - Fate's Twin.