You just can't say no to her smile and the sparkling eyes... And maybe one day she'll abandon the whole sex friend idea and you two start dating - in a sequel!
See what tends to happen when perfectly natural sexual curiousity is repressed ... at least Tanaka-san proved to be decent enough not to (*cough-cough*) "take advantage" of Sakurako while she was momentarily 'incapacitated' ... far better that, once she's re-educated on these things, he can go ahead and (a-hem) "take responsibility".
It's always the innocent looking ones, isn't it...
I can respect the guy though. 'Shouldn't we be having sex now' and 'We should, because it's normal'?
He knows his Hentai situations as well as what should be happening...and he certainly wasn't afraid to go for it!
That ending though! He seemed so hopeful that he got a new girlfri...Sex friend though, according to her.
Well, just do your best to one day move the relationship forward, I suppose.