itch.io

I assume you have Rune's porny scene outside unlocked, with the dog dong?  You get an access to this scene at the end of your playthrough if you saw Rune's mana balls in the bomb investigation scene (by being patient and never whacking him when he bothers you)

You unlock the human dong alternative version of that scene when he asks you to help him with the one-on-one research and you REFUSE. ;)

The game itself gives you hints by simply playing it to the end.

If you're still having trouble, then please come back here with which part you're stuck in.