Late on night, Shūsuke spots a sexy cosplayer named Ran Yatagai on top of a vending machine. He later sees Ran, who calls herself Princess Leila, at school the next day, who invites him and his friends to the rooftop. She claims to be seeking a saviour amongst the scum of the Earth in order to defend it, with Shūsuke and friends believe to be initiation for some kind of underground club. As Nao and Iroha decide to follow her, they meet her twin sister, Rin, who reveals Ran is using her own peculiar method to find a partner. While Rin manages to scare off the other AGE explorers, Shūsuke goes alone to an 'awakening ceremony'. Shūsuke is scared off by Nao's presence and runs off with Ran, who decides he is her saviour. Meanwhile, Rin appears and shows romantic interest in Nao, now that Ran is preoccupied.
Nao Takanashi loves her brother ShÅ«suke despite the incest taboo. Nao thinks that ShÅ«suke is her blood relative, but in fact she is an adopted daughter, whose parents have died. After Nao learns the fact, she wants to fall in love normally with ShÅ«suke because siblings by adoption can marry under the family law in Japan. However, she finds herself competing with ShÅ«suke's childhood friend, Iroha Tsuchiura, and his class president and yaoi lover, Mayuka KondÅ.
