Like um... I need a sequel.
A sequel for people who can accept Haru and Midori's romantic relationship without labeling it as pedophilia....because it's not.
Kinda the reason why Haru moved in with her aunt, cause she knew she would need to become an adult in order to live together with Midori, rather than be treated as a child that needs to be taken care of by the person she has come to love.
Oh my god, you put this so well, I'm convinced! If I were in charge, there'd only need to be 2 more chapters for this to feel resolved in a much more satisfying way.
Anyway, I've sort of been on a non-romantic partnership kick lately, with "Lillie's, Voice, Wear Wind" as my last stop (I won't get into my slight gripes here). I'd like to say that I think the urge for people to place their love firmly in mother-daughter or romantic is misplaced. It's a love that with age may very well sprout into romantic love, but is definitely separate. The characters don't label it for a reason: it's a deeper love than mere friendship, it's more equal than parent-child, but it's not (yet?) a shared romance.
I think one way to take the story is that the younger Haru may have felt the need to grow up—especially apart from Midori—because she understood that while they both held each other close, Midori could not think of her in a romantic way because of her age.
Another way is that Haru felt she had to grow up to get past what you describe: Midori feeling obligated to distance their relationship behind a parental/mentor lens, on display in her inability to ask Haru to stay. In this scenario not because of a crush, but because of the aforementioned unlabeled partnership love.
I've had similar experiences myself as a kid who matured quickly. Entirely on the friendship side to be clear, not romantic.