Wow, what a coincidence that he just so happened to take an interest in her armpits, leading to a perfect hentai situation.
Great ending though. If he's going to keep catching her in the act, may as well just take her in...in a more permanent fashion, perhaps?
And in due time, the statement will be made to their friends, their families, and one fine day, their children: "And that's how we knew we were right for each other."