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.
Ritsuka's world shatters when his older brother Seimei is murdered, leaving him with only his unstable mother and a void he can't explain. At his new school, a beautiful stranger named Soubi approaches him with cryptic words about the past, claiming bonds that shouldn't exist. As Ritsuka pieces together fragmented memories, he learns a disturbing truth: he and his brother were part of a hidden system where paired fighters battle in shadow, one protecting while the other sacrifices everything. Now Soubi has become Ritsuka's fighter, bound by rules the twelve-year-old barely understands. Together they're pulled into dangerous encounters with other pairs, all connected to an organization called Seven Moons that orchestrated Seimei's death. Ritsuka's investigation into his brother's murder becomes a descent into a world where love and violence blur dangerously together, where trust is a weapon, and where the answers he seeks might destroy what little remains of his humanity.