So... the author's gotten a collab with the 30th anniversary release of Nirvana's In Utero. Looks like a promotional sticker from a pop-up shop? Twitter translate isn't the best.
And the timer is active! No matter how Mitsuki meant what she said, Aya's going to interpret it either as her doing something wrong or feeling like Mitsuki's made up her mind to go to America. This might be the inciting incident needed to get her to confess how she feels. Perhaps after a few more misunderstandings and a growing desperation making her say it out of a final panic to get her to stay, even if she never planned to go anywhere...
You can give her as many wacky reactions you want, I will never like Kaoru. She's been a trash-human basically this entire manga and no amount of character growth or goofy faces is going to fix that for me.
A flustered Mitsuki in a swimsuit will be even better. Are we gonna have a panel after the swimsuit reveal where the other two girls in Aya's squad are just deadpan going "I understand now." and wishing them the best on their inevitable marriage?