My Hero Academia

I strongly advise either write the characters either after the series where they'd all be adults or change the setting from an high school academy to a college.

As for ideas...

A kiss-based quirk. What else for a story like this?

One could transplant Fuuka from Naruto into here. Just alter her Execution by Kiss ability where she can steal chakra and techniques to one that can steal Quirks and energy.

Or give Izuku the ability to boost another person if he can kiss them. With One-for-all also in him, that can be a powerful boost. He'd probably be in trouble if it also really pleasures whoever he kisses.