hmm, I feel the jump to sex was a little rushed, like there wasn't enough building of their relationship.
but the art is great and the girl is cute, so i'll forgive that little gripe.
Said it before, saying it again - it's not always just about "T", "A" and "P" here at FAKKU; sometimes we can really come across something here which "broadens our minds".
It's pretty clear that Maruko conspired with Izumi, in order
to lure Taira to Maruko's place. She needed a strong man,
all right, but not for spring cleaning (which was just a ruse).
Man-Of-Culture Scores Happy Fun Time with Sexy Onee-san Senpai (possibly, third-party played part of Wing-Person by not showing up) ..... AND IT IS GLORIOUS!
Taira's reaction on the last page is odd, because (on page 5) he certainly seems
to spot the mole, which draws his attention to Maruko's ass. On page 5, panel 3,
he's clearly thinking things over, and considering his erotic options.