The guy goes in a mission to bang every girl in the husband's life. Next time his daughter, the time after that his mother and should the daughter ever get a girl he'll be ready too...
Hmm, well, considering a lot of the hentai I've seen up to this point, he didn't exactly have the wrong idea, trying to use sex to get her to fall for him.
Too bad that this time, she just loves her husband more than the pleasure of sex, which I find rather interesting. It still happened though, but he got beat up by that ending anyway. (I find his last question quite valid though, why DIDN'T she?)
NEVER,EVER... Think you have the upper hand with a woman in any situation!! I get the feeling that "old man misery" is just getting started with that guy...