ISUCA

Strange things start happening to Shinichirou Asano, a second year student. A woman turns into a centipede, and he sees a girl is attacked by a monster. During all the chaos, he runs into Sakura Shimazu, who uses a bow as a weapon. She is the 37th head of the Shimazu family, tasked with ridding the world of monsters. Shinichirou and Sakuya end up fighting one of the monsters together, when Shinichirou accidentally releases one of the creatures that Sakuya captures and they cooperate to catch it.

Shinichirou becomes friends with Tamako, the cat-monster, and ends up helping Sakuya clean, as she lives alone. Sakuya is bossy and doesn't give Shinichirou a break. Another monsters appears at the school, which takes girls underground and eats their flesh.

Sakuya's younger sister, Suseri, shows up. She also works to rid the world of monsters, and is a rival to the head of the Shimazu family. She wants to bring Shinichirou over to her side, so she attempts to seduce him, and eventually kidnap him, but they run into a bit of trouble with monsters on the way...

There's been a ghost samurai going around killing a bunch of people near the school, but why is all of this happening around the school? Everyone thinks it has to do with Western magic, but what does that have to do with Sakuya?

Shinichirou has the Eye of Truth and it allows him to figure out people's true names, but Sakuya doesn't want anyone to know her true name, so she's keeping Shinichirou away from her.

Shinichirou tries to cheer Sakuya up after he finds out that she might lose her right to become next head of the family. The secret behind Sakuya's birth, and why she's so hung up on taking over the family becomes evident. But then a monster shows up which will test her allegiances to the past, to the present, and to herself.