Future for Sena Riku

I believe that this brutal against Suzume will set up Riku's development as a character and a fighter. She definitely needs to learn martial arts, as she definitely lacks her sister's natural strength to make her thug fighting style work further in the story. She was pressured mostly by grapling attacks, which can be avoided by keeping your distance with kicks, which she is already pretty good at. I would say with my limited knowledge in martial arts something like Muay Thai or Taekwan-Do would suit her pretty well. But what do you think? How can Riku become stronger? Who can be her potential trainer?