Shinobi no Ittoki - S01

Ittoki Sakuraba doesn't get why his mother, his uncle, and his childhood friend Kousetsu treat his safety like it's such a big deal. Kousetsu is always following him and watching him, ignoring any sense of privacy, devoted only to keeping him safe every moment he's awake. But the constant hovering starts to make sense when an adorable second-year at his high school, Satomi Tsubaki, asks him out on a date. What seems innocent at first turns out to be something else when Ittoki visits her house; she means to kill him, and she isn't working alone. The ones who show up to help him, surprisingly, are his uncle and Kousetsu, dressed in their dark, deadly ninja gear. Once Ittoki is brought to safety, his mother tells him the truth: he is the 19th heir of a noble ninja clan called the Iga, and a rival clan, the Koga, wants him dead. To defend himself against this new threat, Ittoki has to sharpen his skills at the only ninja academy left in Japan: the Kokuten Ninja Academy.