I imagined this as a supernatural GxG plot. I dunno, something about a badass female duo who trains MMA sounded a lot more interesting than a boy and a girl doing it. To clarify, MMA "Mixed Martial Arts" is a competitive sport that combines all kinds of martial arts for striking (punches, kicks, knees, elbows) and grappling (submissions, takedowns, ground control). This roleplay would involve a lot of physical combat in tournament matches, training, sparring and perhaps if a conflict comes up. Outside of that there would be conversations, hanging out, and new story elements. As for the plot...
Clair, a 20 year old woman, has been training in martial arts since she was 13 years old. She started out with Judo and eventually pursued fighting for sport as a consistent hobby. She loves the competitive nature of MMA at 15 and couldn't get enough. Her favorite part of fighting this way would be the wide array of strategies she could use for different opponents. Recently, she became an assistant instructor at her gym and knows everyone who practices in her class. She is very kindhearted and willing to pass on the things she has learned. However, in a match she is fierce and fully engaged. She has knocked out opponents before by nailing the right spot or choking out those too stubborn to tap, but still tries to avoid being brutal.
Lately she has been feeling somewhat bored, because the tournament isn't for awhile and nothing interesting has been happening at the gym. That is... until a new girl shows up.
You can decide how your character will be, here are some sample ideas: