The First Time With My Childhood Friend...

Denser than a brick wall

Osananajimi vanilla PERFECTION!!!

Another time and place, a discourse like this might have happened afterwards:

Ryou: "I didn't expect some kind of Parent Inquisition!"

His Parents (bursting in to jarring musical chord): "NOBODY EXPECTS THE PARENT INQUISITION!"

But Seriously, it's more often than not that children tend to forget that their parents were once teens, too, and were probably just as horny during their first time, too. At least they seemed to know better in this case, not to interrupt. And just maybe, Narumi's parents might have sensed "a great disturbance in the force" at that significant moment, also.

Nice One, artist-san.