Hi, Good Morning. It's me again and I apologize if I did get annoying now ♂️
I have reread your story "You're My Best Friend" while having to think of an idea that could somehow spark motivation and inspiration to you. Yes, I know I get annoying at this point but if you would consider my idea that I have come up, it would be highly appreciated. So right now, both Haru and Rina have meet their new friends, right? Also I think the part where they're not in the same class could be helpful
So here's what I thought, how about making them jealous as they hang with their new friends and gradually shorten the time Haru and Rina spend with each other, shorter time than they already have. There could be a point where Haru sees Tomoya being sweet and nice to Rina, as for Rina who is nice and sweet will accept it, Haru grunts/grits her teeth from jealousy
As for Aina, she could get to the point where she sometimes get touchy to the point she'll lean on Haru or links her arms with Haru. Yes, Rina sees it all and feels jealous everytime she sees that.
Also knowing Mami and Tomo, they would somehow fuel that jealousy within Haru and Rina thru their usual teasings whenever they're together. If what I suggest makes sense in a way haha but it is your choice if you want to add the povs of Haru and Rina