Mabye if there another girl that actually romantically interested in akira it may end up getting a reaction from rumi also feel like akira leaning into like girl more especially when he was thinking does he have to start liking boy just because he a girl now.
Honestly mabye there more of that probability now that she found out akira was a guy before but mabye rumi also scared she ruin there friendship mabye once there in high school we get more progress there.
Wait i just realized this series and Onii-chan wa Oshimai! Both show that the first friend them made as a girl also get jealous when the mc get close to other and have some feeling towards the mc that seem more then just something normal friend have.
I hope it does to spite people like you who just like to act like the whole yuri fan in genderbend are bad, it quite clear it heading that way especially with how they reacted when they got very close to each other nose.