くのいちばんっ！

There is a world famous shinobu village that produced a huge number of subterfuge experts. Main character returns to his home village for retirement. He is asked to make full-fledged ninja out of failed ninja candidates. It's a colorful bunch of different girls, but pride of his art is on the stake. He starts to live with the girls under one roof and train them.

[From vndbreview]