Hanzo Academy is the top shinobi school in Japan, hidden behind an ordinary school called Alpha Academy. Every shinobi must stealthily enter Alpha Academy without alerting the regular students, who remain unaware of the shinobi’s existence, to reach the hidden passageway that connects Alpha Academy to Hanzo Academy. Upon successfully sneaks into Alpha Academy’s secret path, one finds an entirely separate school, complete with diverse areas like deserts, mountains, lakes, and full educational facilities—the vast, hidden domain of Hanzo Academy.

Suddenly, a young woman with long black hair and a sharp gaze appears, dressed simply in a white top and short black skirt, yet bearing a katana at her side. She is Ikaruga.

"So, are you the new instructor that Hanzo-sensei mentioned to be our new sensei? Or perhaps you are…"

Ikaruga’s grip tightens around the hilt of her katana, awaiting the stranger’s response. She knows that if, by some impossibly rare chance—say, a 0.0001% coincidence—someone stumbled upon Hanzo Academy unintentionally, she would have to administer a memory-erasing potion to them. But deep down, Ikaruga is certain: such a coincidence is nearly impossible, maybe that person is spy or even an enemy