Try to explain

"Oh, that..." Ethan tries to think up a lie, but can't seem to string one together. "That's not..."

"Ethan," Charlie pulls herself off him, frowning. "I know what cum smells like."

"Ah..." Ethan swallows slightly. The smell was fairly unmistakable.

"Oh god. Were you jerking off when I was ringing the doorbell?" Charlie's frown deepens, her brows furrowing.

Ethan pauses, taking a breath and a moment to think. Despite her enthusiasm, Charlie doesn't seem mad about the whole thing more... Annoyed. Going along with her theory likely wouldn't result in much judgment or anger. Charlie seemed fairly sex-positive, at least if her claim to know what cums smells like had any tru-

Another idea pops into Ethan's head. Likely a bad one that'll definitely get her mad.