I feel like a conversation of the confession leading to them talking abput their feelings for Keisuke has the most potential for melodrama and pace, unless theyre still gping to want to build up the vibe by making it more vague and awkward between the three (i just dont see it (a scene where the two of them get an awkward vibe) happening between the two girls whatsoever)
I would have to go back and read Otobe's appearances - but I don't think she has any reason to believe that Kusunoki would have hypothetical feelings for Keisuke.
The fact that she seems so nonchalant about talking to Kusunoki about being confessed to makes me think she might not by shy about the concept of romance, or at least talking about it with someone else (Kusunoki being who she is to Otobe probably helps a lot here), so
maybe Otobe might say something like
"I got confessed to, but I need to figure out how to turn them down because I like someone else" in however many words/panels it would take.
Kusunoki says she'll help, and off the back of her convo with those three at the cafe, she maybe asks Otobe who she likes (maybe Otobe having romantic feelings
period is big news to Kusunoki, given they've known one another since they were little), and that's when Otobe bashfully admits to liking Keisuke. If she's hesitant to say the name, I expect it to be because she used to dislike him for getting close to Kusunoki; but maybe she'll come out and let his name slip.
And
that would maybe startle Kusunoki, who's only just now reassessing her own feelings toward the ML - and the question then becomes whether she freaks out and feels like she has to fight for him,
or she decides to lock even thinking about it further inside her and offer to support Otobe in pursuing him.
Either of those feel like effective ways to introduce further drama/narrative tension, especially with Hebikawa in the mix independent of their impending conversation (assuming Keisuke comes up during their talk next chapter, of course) - the only difference being one further sees Kusunoki's romantic arc delayed all the more.