Nice. ^_^
break-up arc is gonna happen at this rate
We must be reading two very different manga...
People get very paranoid about these things.
Mitsuki is definitely not aware of Rinko's feelings, she's just not that observant, and you can see from her innocent expression when she looks back that she has no idea she's dashing the girl's hopes
Which means she sprinted out into the rain because she saw Aya.
She ran through the rain to join her girlfriend under the umbrella slightly sooner.
Like, I get that Aya and Mitsuki need to talk about Mitsuki's music. Mitsuki needs to process her feelings and her upset and she needs to understand that Aya isn't going to judge her. But let's not get this twisted. This isn't a relationship problem. They are as into each other as they have ever been, that was the point of the Narita "cupid" episode.
Mitsuki's problem is a Mitsuki problem, not a MitsuAya problem.
Not entirely sure where all this is going, if the band theory I echoed before is right or not, but at the very least, I don't see anything hinting at a breakup arc.