Ah, schoolgirl refresh...Plus super sadistic option.
Hm. Well, I could feel some Vanilla feeling bits especially when she keeps saying it's an option only for him, or something, but in the end even he says that she'd probably just use him as a plaything again...Not that he seems dissatisfied by that.
For the chance to be with a babe like Yuri, I suspect most males, even though they never thought of it before, would develop "M" tendencies on the spot at receiving "an offer they couldn't refuse."
Luckily (call it the luck of a hentai protagonist) there seemed to be a level of mutual interest (if not all-out attraction) between Yuki and Takkun. Perhaps his leaving his phone behind was his subconscious seeking to set up an (*clears throat*) "encounter", such as took place from Page 6 to the end.
... AND IT WAS TOTALLY WORTH IT (Takkun, you Lucky Bastard ... GRR!)