I like Akira. I like her boyishness because I'm biased, but what makes it good is that it's mixed pretty well into her person-- I don't readily think "the tomboy" and then roll my eyes when I think of Akira, and the narrative doesn't try to force you to identify her as such entirely because she has short hair, wears boy clothes, has a unisex name, and uses 僕 in self-reference. The reason why I'm saying this here is because this is the first chapter where she indicates that she in fact has "girl" instincts on account of indeed being a girl (see p. 7-8) that squarely does not do anything for or against her cuteness; she shows "shy girl" instincts in chapters 6 and 7, but that's clearly meant to make her cute on top of maintaining that character trait. Currently, I figure her boyishness is either a metanarrative pointer to the fact that she's a daddy's girl, or is the direct result of that.
I like the MC and his unusual resolve, as well as his philosophy of "Mendel's laws have nothing in common with blood". This could be a story where the most he does is bear his boyish stepsister's seduction, but he sincerely wants to make this blended family work out of care for Akira and also because he was burned by his own parents' divorce. That wound leads him to proactivity and feats of courage like advocating for Akira and speaking against her father's intention to exit her life. I also like that he barely considers his childhood friend human (it may or may not be realistic, but it's mildly entertaining and the mutual assholery lends a pleasing chemistry between the two).
What I worry about, at this point, is how Akira's affection is going to be handled in general. She really switches from being shy around the MC to being this ultra-competent tease in the very chapter the MC finds out she's a girl (ch. 5), literally four panels after she proposes they carry on as they used to. She says she wants to be like brothers, and then she mounts and strips on top of him not even two minutes later. In this chapter, she's mounting him again and she's proposing that they graduate from step-siblings to spouses in the future.
That's why my current impressions ("barely above average but with charm", "has potential") are what they are. What I just described? I liked it inasmuch as it made me feel good. I like tomboyish and tomboy-adjacent characters that aren't just a jerry-rig of superficialities meant to signal "tomboy". It's cool when they worry about stuff like being "girly" enough because they're used to freely gravitating towards what they're comfortable with at the cost of not fitting in with other girls and maybe being too plain for the boys. And there's the potential for very striking displays of libido. It's not even that her attraction developed too fast overall-- it's that this is the second time she's gotten sexually hyper-aggressive out of nowhere. It makes sense here partly because she's reacting to the threat of Hinata probably liking the MC, but mostly because I already saw her act like this in chapter 5... but it didn't make sense there because she was just talking about being like the brothers the MC thought they were mere seconds before she mounted him like a horse-- I still can't reconcile the "before" and "after" on that, even if I supposed she just initially lied or she became aggressive to hide her own embarrassment. Even if it's supposed to be another side of her, it's hardly ever remarked upon for what's a diametric change in character, and it's very clear to everyone and the reader that her subsequent "training" is casual seduction.
This is the one character quality so far that feels like it's poorly integrated into her character, and it's a big deal for me even if I like it when she gets like that. It's like she's teetering between "dimensional character with a crush on her stepbrother" and "what are you doing, step-bro?" at all times. I don't want this to definitively become a rom-com-drama slog where the heroine's an avatar of lust whose sole purpose is to inspire the feeling of >tfw no tomboy gf in the reader.