For one, sure if you scratch the surface of his neuroses enough you might find negativity over feeling stuck in the same cycles, because of how formative they were. But on top of how deeply rooted it is, and with the way he has cognitive dissonance over who Nozomi is, there's a part of him that genuinely considers her to be a different person- and does find her very different when he's observing well enough.

For another, I don't think his and Karua's relationship was truly static even if it had (potentially serious) issues. There was some development going later on in the memories- Takumi being more responsive to her whims instead of dismissive the way he is in gradeschool, and Karua declaring she'll be the one to help Takumi out of trouble, effectively reversing the promise (the dog memory). It's just that there was no real help for Karua while she latched onto Takumi, who is not a therapist, so she reverts to begging for the promise, hence the 'damsel effect'.

For one, it's the vibes. It’s the feeling that permeates his background in a way that I feel like doesn’t happen for any other- the sneaking feeling of 'is this really normal' underneath a mask. And sometimes that's enough, especially when the introduction shows self-esteem issues- emotional neglect is one thing that's very much deniable to the sufferer, as well as being hard for other people to notice just looking.

Also, the thing about 'normal' is that it's basically 'all you've ever known', regardless of whether or not everything's 'all right'. So you can have lots of photos that look like everything's fine, but every now and then there's one that looks strained, like the subjects are trying to mask. And, of course there's an explanation. Ex: 'It's a formal photo. That toddler is just sleepy. The sun's in that boy's eyes. It was a bad shot of the mother. They She didn't like that dress.' Except it sticks out like a sore thumb doesn't it? Why are there happy(tm) photos where no one is happy?

In Takumi's case, we see 'snippets' of his mundane home life, with one indicating a wall between him and his only close friend while at school. It could be that he was just annoyed with her that day, or a sign that he was becoming strained around her and he needed space- space to grow, beyond the promise and being the 'psuedo-dad' for Karua. This would be less a matter of his story, were it not apparent that Takumi's codependency problem can extend to the role of Team Leader later, starting from when he cowed into it after awkwardly taking praise.

It's also telling how his authority figure keeps him tied to his 'would-be romantic interest' - similar to how Sirei uses her as motivation - likely since he was very young. So if it happens that young Takumi was strained, he might have had no means of escaping that other than to dissociate early on, while dealing with swathes of his own neglected emotions. It's a basis for him being emotionally disturbed even before being brought into the war, which could explain the 'out of pocket' extreme, suicidal behaviour and self-harm ideation when he is.

The way Takumi sees it, the sirens and their reason for existing are just 'how it is'- and if he has questioned this state of affairs before, he's shut down and rationalised it over the years, something that makes him vulnerable to passive acceptance. Which would follow that the same extends to his own life, with him being at a loss for a point of reference. More importantly, he seems to have cognitive dissonance over the 'normality' in his life vis a vis him and Karua- a part of him knows well that their relationship is not normal to others, but he doesn't seem to interrogate that belief to any real conclusion. Such as, what did that mean? Was it healthy? Was he really the person he wanted to be?

Rather than 'are we normal?' Takumi needed to ask 'are we okay?'