Rika has loved her cousin Mao like an older sister since she was little. When she gets to her age, she starts asking Mao for advice that she wouldn't even be able to tell her parents. Mao is gay and came out when she was 18, and now she enjoys love and sex with same-sex partners. Rika, who is jealous of her girlfriend Mao, gradually begins to recognize her as a more special person than before...
