Act like his girlfriend.

"Great! You can start by acting as my girlfriend, nheh heh. Pretend that we've been secretly dating for months now." He then started mumbling a bunch of ideas of what to do with his new 'girlfriend'.

Celestia didn't bother to hear what she was saying. She was too busy resisting the urge to hit him in the head with her backpack. There was a chance that it would give him amnesia and she could avoid dating him and avoid going to jail, but even for the Ultimate Gambler, it seemed too risky. Sometimes the best gambler knew when to quit.

Instead, she did a curtsey and said, "Very well. I, Celestia Ludenberg, will be your girlfriend. I will now take my leave."

She tried to walk away, hoping Hifumi would be too distracted to notice and make more demands of her. Instead, she felt him grab her ass with a chuckle. "Oh no, as boyfriend and girlfriend, we'll be spending almost all of our time together from now on. Now lets see... what should we do first..."