I'm on a weird TDBK kick rn and decided to go through all their scenes again. Starting with Shoto's POV, from Chapter 10-
1. Chapter 10
First time Todoroki speaks or says or does anything, it's to comment on Kacchan. He sees him, admires his technique, and understands exactly what he did. Also, unlike the others in A who generally see Bakugou here as an asshole who's out to seriously kill Deku, Shoto sees only a clever strategist...
2. Chapter 19
While it's not entirely clear if Shoto is reacting to the ice breaking or to the threat here, I think (given how protective he is of Kacchan later) this can count as him looking absolutely horrified at the threat to Kacchan's life. He barely knows him at this point, but he already cares about his safety.
3. Chapter 25
Shoto is pretty focused during the race on winning. The only person he not only looks back at but takes the time to observe in detail is Kacchan. Not even Deku, who's his rival at this point and who starts surpassing him, since he focuses instead on "This path will end up helping the others" after Midoriya passes him and Bakugou.
4. Chapter 25
He also gets caught up in competing with Kacchan in a way he doesn't with anyone else.
5. Chapter 35
Shoto is not shown watching Deku vs Shinsou or anyone else's matches. The only person whose matches he consistently is shown watching are Kacchan's - and for no plot related reason other than to show us that Shoto is watching him. This is the match with Uraraka. Shoto has no real dynamic with her. He's watching here because - it's Bakugou.
6. Chapter 36
Again, Bakugou vs Uraraka. No plot related purpose. Just Shoto watching Kacchan, because he's interested in Kacchan.
7. Chapter 42
And a third time. Bakugou vs Tokoyami and the future title match.
8. Chapter 42
Shoto displays an understanding of Bakugou. He notices how alike he and Midoriya are and realizes Bakugou is echoing what Deku said too.
9. Chapter 42
He's paid attention enough to realize that they're childhood friends and asks Bakugou for more info. No hostility towards Kacchan for yelling at him.
10. Chapter 43
At the start of their match. Shoto is in fact very focused. He gives Bakugou exactly what he asked for, a full scale attack. He's still conflicted, but it's only a conflict because he both WANTS to do as Bakugou asked ("I'm sorry, Bakugou") and because he respects Bakugou enough to know going all-out is necessary. He didn't have the same conflict when fighting Iida. Not because he doesn't respect Iida at all, but because Iida isn't Kacchan.
