Kunoichi no Ichi! no Ni

High school student Ichi visited a ninja residence on a school excursion and was caught in a strange structure during the tour, slipping to the ninja world. Along with his friends, Ichi who got the "Ninpocho," a key to return to the present age, returns safely to the present age. However, suddenly, a surprise appears in front of Ichi who lives a peaceful life...!? (Source: Shueisha, translated)