A twelve-year-old inherits his dead brother's lover as a supernatural partner, and somehow this becomes the most honest exploration of what it means to be loved that anime has ever attempted. The show refuses to explain itself clearly, which sounds like a flaw until you realize that confusion is the point: Ritsuka and Soubi are trying to understand each other in real time, and so are you. It ends before the story finishes, but what it leaves you with is a kid learning that being vulnerable doesn't mean being broken.

Twelve-year-old Ritsuka Aoyagi is left with only his unstable mother after his brother Seimei is killed, and he also suffers from amnesia. On his first day at a new school, a stranger named Soubi Agatsuma approaches him, saying he knew Seimei. In this world, battles are fought by pairs: the Fighter attacks while the Sacrifice takes the damage. Soubi was Seimei's Fighter, and with Seimei gone, he now belongs to Ritsuka. When Ritsuka learns that an organization called the Seven Moons was behind his brother's death, he teams up with Soubi to find out what really happened, and the two grow closer than either expected.