In the universe of Loveless, everyone is born with cat ears and a tail, which only disappear when they participate in sexual activity. As a result, they have come to represent virginity and innocence. Fighting is also limited to "fighting pairs" or couples, with one serving as the Sacrifice and the other as the Fighter. The first takes the harm, while the second assaults. Ritsuka Aoyagi is a 12-year-old child who has amnesia for unclear reasons. His brother was just died, and as if his life hadn't been difficult enough, on his first day at his new school, he is contacted by a stranger named Agatsuma Soubi, who claims to have known his late brother.