Hinako and I are happily married and dream of having a child, but I suffer from a serious problem: I cannot ejaculate. When I confess my anguish to my brother, he asks with a sly smile whether I have heard of having another man father the child. With no other option, I entrust Hinako to my brother, who shares my blood type, for one day. I ask them to do it only once, but they keep having sex again and again throughout her most fertile day.