Hatano Yui is married happily with her husband, a very serious workaholic man who is working too much. He also hates children and has begun to ignore her wife.
Hatano also lives together with the father-in-law and old man who is a more cheerful and would love to have children, plus he pays very good attention to Hatano Yui, or in other words, what the son lacks the Father has plenty of… even sexual desire. Since their needs match, it comes to happen that they decide to make some children while the husband/son is away working…
