Kusunoki isn't perfect, she puts in a lot of effort...but she's not shown struggling for longer than about 3 pages and usually immediately succeeding (or at least close enough) after so I can see people getting that impression.
She was selected as the lead for the play but put in a ton of effort and learning to dance with Keisuke. But that was all montage'd away and the end result was her being completely perfect. She's shown studying a lot and studying with Keisuke, but again that's all practically done off-panel.
And as you mention, she's shy and constantly worried about others' opinions and being rejected and left out.... but as soon as she talks to people they immediately accept her. Even her outing with Hebikawa, she charmed the snake so hard she's dedicated herself to finding Kununoki's dark core (challenge level: impossible). In the play, she goes with the flow for a while and then when she steps up to a course of action (suggesting Irma be the prince, giving her a pep talk in to the bathroom) it immediately works. which undersells the scene because it was cute seeing her think of and channel Keisuke. And while not everything needs to wall-to-wall angst that was way too neat of a wrap up
I guess imo she's a good character, but she's not being used effectively.
I do agree she's conquered her initial challenge with the play and now getting in with Irma-chan's friends.
I'm also going to say: Otobe is being set up for a "what do I do when I'm a third wheel to two people I love dearly?".
Hebikawa was initially refreshingly boring; being set up as Keisuke's traumatic origin, she "For me, it was Tuesday"'d him. Now she's being set as a dark villain again.
Both of those are stronger cases for interesting interactions than "I just don't know if this guy obviously crushing on me actually likes me...." when she's just a normal SoL protagonist.
She puts in effort - but at the same time, it seems implied that the same amount of effort put in by others amounts to nowhere near the same amount of success.
When she studied with Keisuke for the test after asking his help, he gets a 95.
She gets a 100.
When they go to play Dodge Ball, and Volleyball at the beach, and the soccer game with Otobe during the flashback - she's effectively athletically gifted. During the volleyball game she and her teammate don't break a sweat and Keisuke and his teammate are gasping on the ground. During the childhood soccer game, she blocks
every goal coming her way, to the point that Otobe accuses the boys of going easy on her. And during the Dodge Ball game, she 1v2'd Hebi and the Huge Dude, the latter whom was responsible for ejecting a bunch of her teammates - and she just solos them both?
She frets over what others think of her, and the two most recent people who were actively unsure and leery of her, fell in love with her within a minute of her talking to them for the first time, and she just happened to know
exactly what to say to each, and just happened to have the requisite "otaku knowledge", to perfectly win over the one who very much wasn't a fan of her going in.
Yes - she's put in the work. But she's also seemingly been gifted the latent talent of "darling FMC of the author's universe", because
everything she does is a resounding success, with no room for mistakes or minor errors.
So when I say she's been "written too perfect',
that is what I mean. She's not nuanced, and the only "flaw" she's given, seems like it was there to set her up as intriguing for the ML/lens character that is Keisuke, and the moment she actually steps up to something, she faces zero issues in doing it better than everyone else.
Compared to everyone else in the story thus far, including side characters like Irma, she's playing on easy mode. And that doesn't make her compelling as a character, because she's effectively in a different manga/story than the rest, as someone else here mentioned further up the thread.
Honestly the only other flaw that I can say she has is she's aggressively oblivious to romance, which
I first thought was her just avoiding thinking about what she felt for Keisuke - but after the "shipping" question this chapter, it seems like she's just.......completely ignorant of the concept and has no means of relating to it.
Which is a strange way to write the character that is ostensibly the main romantic interest of the other protagonist of the story, especially as she's aggressively shut down all talk about feelings for him, including to his face, this whole time.
Because in reality, there comes a point where he would just give up and walk away from trying, and I suspect he would have if the events of this chapter hadn't transpired, which feel entirely engineered to force Kusunoki back into the mix after pulling so far ahead of the other three.
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as far as the rest of what you said - I actually worry Otobe is going to awaken Kusunoki to those feelings for Keisuke, and the moment that happens, Otobe straight up loses before she even starts. Because Keisuke
will not look her way if he knows that Kusunoki has any interest in reciprocating his feelings for her. Yeah, I know childhood friends lose (shout out to you, Botan), but it almost feels insulting how stacked the odds are against the Tomboy by virtue of who the FL is.
Hebikawa will hopefully see some success in growing during whatever arc she gets with Keisuke. Hopefully they have some time together before Kusunoki comes back on-screen.