Steph!! Sure, they're both sympathetic, friendly, and with strangely high tolerance levels for grumpy/closed off characters... but also Hibiki is a dummy, so if you'd like to be friends with the brightest genki girl you'll ever meet, by all means.

Also potentially things can be done with Hibiki's secret identity? Seeing as she's... now a famous singing superhero idol. I've got no ideas concerning it, but still, its out there.