Imagine Chara being so fascinated by the number "9" that she only allows horny times to end when it's been reached in some capacity...Like she must leave 9 kisses on you (so if she has lipstick on, everyone can tell you're very affectionately loved), or just make it where all competitions are a best-of-9 type thing. Or maybe that someone has to cum x9 times for her to feel satisfied if not a collective x9 orgasms. Maybe when thinking about kids she plans for a really big family of 9 kids.