Summary by Wrathkal
Anon is shaving one day (with an electric razor) when Reimu blushes and calls him perverted. No matter how much he asks her about it, she won't say.
He recalls that Reimu sometimes rubs her body against the washing machine as it's running, going 'yufu~n, yufuuuu~n', but doesn't understand what's going on. Story ends with Reimu relenting a little about letting him 'do it', and Anon still confused.
ED: For those who don't get it, think vibrator and where the penis would be if humans had yukkuri bodies.