As a retiree, Old Man Tetsu desires nothing but lives a quiet life in retirement. All his children already have families of their own, and once in a while, his granddaughters come to visit him. He adores all his granddaughters to bits, and he is at his happiest whenever they come to visit.

Of course, that doesn't prepare him for the fact that all his granddaughters are fantasy heroines. Magical girl? Demon hunter? Battle nun? It seems that Old Man Tetsu is going to have a rather interesting life in the coming days. So much for a quiet life in retirement.