It's honestly really annoying how few people recognize a traditional "bancho" outfit. Hell its not even the first time Osonada has been drawn wearing it. Potato is far from the only character who dresses like this, guys.
Super late to reply, but you're correct. She may be crazy good at fighting, and she may have been part of a huge gang — but, at her core, Raino is just an ordinary girl that wants to enjoy a happy life at her school and have fun with her youth. Just like Rokudou. So, her still liking him now is basically confirmation that her feelings aren't controlled by the mark.
She doesn't have a hidden switch to go crazy, like Azami does with motorbikes. I'd say Raino is tough outside, but as soft as they come on the inside.
...And our boy still rejected her confession, fuck. I get that his true love is Ranna — and I like Ranna too — but I was really rooting for Raino.