Hermione creates a potion that makes Ron produce more semen. He sneakly takes the potion and has the WHOLE bottle, when he was only supposed to have only 2 drops! Hermonie laughs at him when Ron shows her the damage, his balls look swollen and about to burst and his cock was as huge as ever. She ends up helping by making him cum and tries to leave, except Ron has other plans of making Hermonie drain his balls fully until the potion has worn off. 

He uses a body control spell and has full control on her body. When she tries to leave Ron makes her undress and leave her socks on. She is so embarrassed Ron has come to this when he could have just asked her to do this! He controls her body and makes her suck his cock and slap her tits, she then grinds her ass on his cock and he cums again on her asshole. She thinks this is the end when really, it is just the start of Ron's plan for her to drain him. She is then riding his cock feeling ashamed and angry at Ron and she begs him not to cum inside her, he doesn't listen and does it anyway. 

The spell soon wears off and she tells Ron that she will never let him get his hands on the potion she made ever again!