Well damn. And here I was already thinking about the dangers of their little kinks and fantasies once put in practice. Thinking back on the panties-selling incident with the gross dude, even if Shirasawa reacted well, he needs to make sure they're always discreete and that Honjou is safe if they're playing outside. I mean their little bubble is lewd and cute, but outside of that it's crass and mundane enough for it to burst if not careful.
But the danger came even before that. The sister was a clear dick, but I gotta admit that when Honjou said 'I can explain' I thought 'Pls, don't explain, it's actually worse XD'. Might be age starting to show, but I put myself in the mother's shoes and this deserves a mild freak-out tbf. Remote vibrator in the handbag of your 16 yo daugther. But nothing more, nothing less.
Though Honjou is right of course. It's not disgusting. Parents chastising their children for natural impulses is always so hypocrites when they're literally standing in front of living proof that they get freaky too.