So the Touya-Shouto conversation went like this - slightly paraphrasing here:
Touya: typical, dad didnāt show up again, only sent his annoying brat and 3 minions.
[insert background noise from sidekicks]
Shouto: are we doing this as bros? Or maybe not?
S: In any case, Iām not here because of dad. Iām here because I want to be.
T: still makes you a puppet, lol. Except you are also too dumb to realise.
S: if I ghosted you, that would make me a puppet (burn, dad, not gonna name names)
T: OK, good point. (But who keeps a score? Me, thatās who. Gonna quickly start a monologue here so we both forget that you had a valid point) In the end, we are all just humans with our issues, except our coping mechanism are expressed with crazy quirks. Thatās super-human society for you? See? Toga and Spinner like to stab things, Shiggy is all destroy-destroy. Me? My coping mechanism is to burn shit. (Did I make this sound philosophical enough? I bet you donāt have a come-back for that little brotherā¦)
S: Anyways. Why didnāt you come back to us? We missed you.
T: (why are you like this? not gonna cry, totally not gonna cry) glad you asked. We are family after all and your big bro likes to talk. (I wanted someone to ask me this for so long and itās more fun talking to you than old ballsack face)
T: also, my fire is still better. For the record. š
S: your face is melting off
T: not the fucking point.
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Shouto really managed to engage Touya enough that he went from thinking of Shouto as āEndeavorās Third sonā to acknowledging their brotherly bond.
But still, Touya mostly relates to Shouto in terms of quirks - calling him masterpiece, comparing their fires. He still sees both their existence defined by Endeavorās experiment.
While Shouto - I feel even if he tries to remind himself that this is in fact Dabi, the villain - treats it mainly as a family issue by dropping the most important question. He doesnāt care about Touyaās quirk upgrade or who is hotter (even if Touya is hotter, we all know Shouto is cooler), he cares about why his brother never bothered to contact them. And his expression shows that it hurts him.
In the end, they both know this is about family, and maybe Touya will realize that there is someone who is watching and paying attention. (Even if itās not dear old dad. By the time Endeavor shows up to apologize, Touya and Shouto will be slurping noodles in passive-aggressive protest)