One could forget the pain with a young girl's cooter in your face. But seriously, any bicycle or car crash I've been in involved pain, not hot sex with japanese women.
Actually, I think her pelvis is below his knees in this position. Now that I've taken a closer look at it, it seems her breasts are right on top of the spokes of the wheel--quite painful if she slammed into the ground with that hitting her chest.
But thanks to the laws of bishoujo games, there's a lot more embarrassment and "YOU PERV!" involved here than physical pain.
comment #40490 Anime Law #385: The amount of pain and damaged caused to an individual is inversely proportional to the hilarity/pervertedness/both of the given situation.
Addendum: This law may be bypassed when the resulting injury is part of the plot or comedy.