He cums from embarrassment

It all becomes too much for Ron. Maybe it’s Fleur’s proximity (she is a Veela, after all) or maybe it’s the constant remarks on his size, or maybe it’s simply that another layer of protection has suddenly been removed from him, but whatever the cause, Ron spontaneously cums.

He scrunches his face and his hips buck slightly as his puny penis erupts within his boxers. Fleur and Hermione’s jaws’ drop and Ginny cackles as his underwear balloons outward momentarily with the weak **** of his ejaculation before it settles back around his crotch - now considerably more sticky. Luna tilts her head in curiosity, and gives the spunk a sniff. “Hmm, you stink of Nargles, Ron, have you gotten your ‘head’ checked?” The other girls collectively titter and leer at Ron, who sheepishly and weakly reaches for another pillow to cover himself with, knowing all too well that they’ve all just watched him cum without a touch.