Surprised this didn't derail into the other 2 guys joining in and turning the girl into a slut. At least goes to show they are true friends. As such, they deserve their own girls too! So they don't miss the fun.
Pair of Mating Rhino Beetles: "Calling Wingman (or rather, Wing-Bug) Control: Mission Accomplished. Repeat - Mission Accomplished!"
And it's funny how one of Tatsurou's classmates "got the hint" of what was going on way before the other.
Hmm, so those rhino beetles mating was also them being wingmen for our couple, eh?
Still, I found it amusing that her first reaction was assuming he got off to beetles mating.