@Graywing
It was foreshadowed a bit, but most of the hints were really vague (Like that she went to an all-girl's Middle School, she said she was happy to be complimented by Takamine, who was a beauty, she's comfortable not wearing a bra around men, and taking off her shirt around MC, etc.) but those are all circumstantial. Honestly I'd assume it's more likely she's bi because she does hit on MC and tease him about being handsome, say that she wasn't bothered about the boy-girl thing SPECIFICALLY with MC and that she doesn't mind as long as it's him and that she shouldn't lick his neck because he's a boy. Most of the hints are contradicted by other dialogue or events which makes the whole message kinda muddled. (Her actions definitely make it seem like she's lying about having just a friendship with MC because even the closest of friends don't lick one another on the neck, get all touchy-feely with one another, etc., though that may be because of the all-girl's middle school.)
I think this falls more into my general criticism about Japanese works depicting homosexuality as less of innate thing and more of something that happens due to exposure and environmental factors for the sake of fanservice. If I were to guess, the reason she's in a relationship with a girl is due to being an amateur model and them not being allowed to be in relationships with men, along with her lack of exposure to men leading to a bias in favor of women, which I don't think is an accurate assessment of how people find out they're lesbians.
@Castafiore
Bruh just let lesbians exist??? Also, you say that like people wouldn't be fed up with the childhood friend cliché if they did that
I do just let lesbians exist, but these character don't exist. (Not in reality, anyway) They're fictional, and so my criticism comes from a writing/narrative perspective.
I do think this relationship was handled better than most other manga, but it doesn't excuse the seemingly contradictory way this character behaves, which just seems not to work if she is already in a relationship with a jealous individual whilst at the same time doing all these things to her "childhood friend."
Also, for a while, I have been asking for this kind of arc where another character gets into a relationship with MC because, at that point, Takamine had basically blackmailed him into being her manservant via a false rape accusation, leading to a moment of introspection of how Takamine treated MC and how she would change her behavior for the future. I don't complain about childhood friends, so don't pin that position onto me. The result of this arc is unsatisfying because it doesn't lead to any character growth or change and felt like a big waste of time apart from the revelation that MC had a childhood friend and that Takamine can get jealous. I don't feel much was accomplished now, and it felt like the author was building up to something better than a big "PSYCH!"