Tomo is lucky. But ironically Ibuki is, in a lot of ways, part of the problem.
Since their childhood, Tomo has admired Ibuki for being "cool" in the traditional sense. Charming, composed, athletic, confident, etc. All wrapped up in an attractive, downright princely package. Ibuki is the epitome of the traditional "coolness" that Tomo wants to achieve and surpass. The coolness that he's been comparing himself to and competing with since their youth.
So on top of Tomo putting himself last and valuing other people more, it's also a case of "we are our own worst critic"; he's so fixated on matching Ibuki's traditional male-coded coolness that he fails to see what makes him cool. And, in fairness, he isn't what people would traditionally consider "cool." He's warm, he's kind, he's sincere, he's empathetic, and IIRC he can cook and knit, too. But he's also short and tends to be pretty goofy, too.
Also have to remember that the President of Ibuki's fan club made it clear that said fan club will not tolerate him sullying Ibuki's image. And yes; "none of their business, not their decision to make, go pound sand," yadda yadda yadda. But appearances and impressions matter a lot in Japanese culture, and because Ibuki means so much to him Tomo doesn't want to make her look bad. And, as established in this very chapter, very few people have recognized (and openly acknowledged) Tomo's own cool points.
So he's in this spiral where he's not cool and feels like he can't handle his own problems, which only emphasizes how uncool he thinks he is and how he feels like he's made no progress in being as cool as Ibuki. And then of course feeling that way also makes him feel uncool and... well you get the idea. Also, we are often very quick to dismiss the words of our partners, ironically because they're so close to us. "You're just saying that," for example. Or because they love us they don't see what's wrong with us the way we do. So he feels like Ibuki is either simply trying to be nice and comfort him, or doesn't really see for herself how uncool he is. When it's really him who doesn't see his own good points.
I actually thought your first sentence about how Ibuki is "part of the problem" would tie into how she is effectively telling him to "get cooler than me like you promised", without verbalizing all the things she lists in this very chapter that she finds cool about him.
Which I would agree with - you raise numerous good points about the subtext and nuance of Tomo's self-image and self-sabotaging, especially in the meta-contextual aspects of this series taking place in, and being made for, a Japanese audience with very specific views and opinions on the roles one should play within a society and culture.
Unfortunately for Tomo, I feel like this will simply be a "time and effort" deal, because it is admittedly not something you can just turn off and/or wake up one day and decide "nah, not doing that anymore". There's a degree of willful declared intent that can work, but that sorta dovetails into "fake it until you make it", and it still requires that the person
seek that shift in perspective and enacting the behaviors to manifest it. Something that, currently, Tomo seems to "fall short of" embodying, as it were.
I do think you raise good points about Ibuki and her overall situation being part of the issue for Tomo, though. It's not
her fault, per se, but the image built up around her, perpetuated by people like those in her fan club and by Tomo himself, are poisoning Tomo's identity. I think it would require a complete re-working of Tomo's idea on what "cool" even is, at this point, because he's also just not going to achieve the version he thinks he should, realistically - as
@outinthegardener laid out in their comment, as well.
Whether or not Ibuki is cognizant enough to spell out that nuance between them, or whether Tomo is capable of internalizing that nuance and reflecting on his own self, I guess we'll have to wait and see on.
But yes. I do maintain that Tomo is
very lucky that Ibuki has been gungho on getting him tied down as long as she has, because if he were to keep this up and flounder, I could see a world where her patience runs out, especially if he just pushes back on any reassurance she tries to give him (however understandable it might be, given the reasoning you provided - it still runs the risk of wearing down someone who cares to the point they give up).