The only reason Riku might consider rinsing off was that he didn't want his hair to turn green. Seriously NOT a sexy look.
Riku hadn't really been worried about Sora's mom saying yet, but he still cheered and weote a note to his mom on the white board on the fridge. Basically 'Sora staying the night. Need pizza' so that she wouldn't try and unfreeze or buy anything too big for dinner. Not that they wouldn't be able to eat dinner AND pizza easily. Teenaged boys and their appitites. Riku's mom sometimes complained that she was raising a bottomless pit. Riku pointed out that he was obviously in a growing stage, as he kept growing out of his clothes.
"I got sleeping bags if we wanna sleep downstairs," Riku offered. It wasn't like they needed a GOOD night's sleep anymore, since there was no more school.