Shinobi no Ittoki - S01

Ittoki Sakuraba can't figure out why his mother, uncle, and childhood friend Kousetsu are so obsessed with his safety. Kousetsu shadows him constantly, watching his every move without any respect for privacy, solely focused on keeping him out of harm's way. The relentless surveillance finally starts to make sense when Satomi Tsubaki, a cute second-year student at his school, asks him out. What seems like an innocent date takes a dark turn at her house-she tries to kill him, and she's not working alone. Shockingly, his uncle and Kousetsu arrive just in time to save him, dressed in menacing ninja garb. Once Ittoki is safe, his mother explains everything: he's the 19th heir of the Iga, a prestigious ninja clan, and their rivals, the Koga, want him dead. To survive, he must train at Japan's last remaining ninja academy-the Kokuten Ninja Academy.