I don't really see rumi and Akira as having a romantic interest in each other. Rather, it's just having that one friend who is totally accepting and caring for you as a person. If it turned into them getting together, I'd be fine with that, but really, at this point it's more about Akira finding their own sense of identity and whether they will be comfortable in their body.
For Akira, I don't think she knows. She's definitely had the thought of "who am I supposed to be attracted to" and Rumi has crossed her mind, as it was touched on in an earlier chapter, but I don't think she's really settled it, and she probably won't until... well, the title of the manga: Until [she] becomes [herself].
For Rumi, it's up in the air. Throughout a lot of the story, she's displayed quite a bit of casual intimacy or attempted it with Akira, and got jealous from time to time when Akira has had casual intimacy with others. There's definitely enough there to think she's had a crush on Akira for quite a while but...
I have a feeling how their relationship pans out will be contingent on how Rumi processes Akira's reveal. I think it's clear from this chapter that knowing the truth has shaken her a bit, though she still cares about Akira. I think whether Rumi accepts Akira as a girl or not after knowing the truth and processing everything will probably decide whether they get together or not.
Given how this manga has portrayed things so far, I wouldn't be surprised it we get a bit of conflict between them with "Akira used to be a boy" being what tips Rumi over the edge into pursuing her feelings for her (like Rumi thinking "oh it makes sense that I'm attracted to her, since she used to be a boy"), and that causing a bit of friction and pain because Akira will want Rumi to accept her for who she is now and not what she used to be - like kind of inverting the roles; once Akira has decided who she current is defines her and not who she used to, Rumi starts pursuing her romantically based on who Akira used to be instead of who she is, and overcoming that hurdle being the last thing before they get together.