Back in senior year of high school, some dude confessed to Koga.

"I've... always thought you were cute. Can we have sex?"

"I'm a guy."

"I know!"

"... Fine. You're cute enough. My cock is rather big..."

Koga is picky. If you'd ask him about his first time:

"Dunno. Not manly enough, not hairy enough. But in terms of anal, he was... passable. "