Ryōta spent years staring at the sky to keep a promise to a dead girl. When someone who looks exactly like her walks through his classroom door, the show doesn't let him have the catharsis he's been building toward, it hands him a refugee with abilities and a body count, and asks if he can love her anyway. The magic doesn't matter. What matters is that he has to choose between the ghost he's been faithful to and the real person standing in front of him, and there's no good answer.

Ryota has spent years staring at the sky, bound by a promise to a childhood friend who died in an accident. As the only member of his school's astronomy club, he keeps watching the stars in the hope of proving that aliens exist. Then Neko Kuroha transfers into his class, and she looks just like the girl he lost, with a name nearly the same. But Neko is no ordinary student. She is a witch with supernatural powers who has escaped from a secret research laboratory. People are hunting her, and as Ryota grows closer to her, he is pulled into a deadly world where scientists pursue the lab's runaway witches. Neko is not the only escapee, and Ryota takes it on himself to protect them from those trying to drag them back. The show blends drama, mystery, fantasy and science fiction.