Yuu's confession makes more sense the more I think about it.
Yes, we have her worrying and doubting at the start of the chapter over the timing of expressing her feelings, about how it could potentially interfere with the work they have ahead of them and the dynamic they've found & enjoyed up to that moment. And it's a fair and valid concern; Yuu can't be sure what Haru is feeling, and if even the chance exists that Yuu's specific type of "love & like" for Haru isn't reciprocated, it's a forcing of those feelings, in a sense--and that can screw up the dynamic between two people, however close of friends they are. If Haru didn't feel the same way, she'd still try to keep things going between them for the sake of this competition, but it would be there, sticky between them, making everything awkward and each overly careful of the other.
Which would, in effect, ruin their relationship over time.
But, once Yuu saw Haru's notebook and lyrics, I think the wording coupled with Haru's mention(confession?) of writing "from personal experience" was the first push Yuu needed. She's very perceptive and insightful with the right setup, and the smattering of lyrics she initially saw would have put the idea of mutual feelings into her head, at least to a degree. She is the person who has allowed Haru to grow beyond her old limitations and step into a world that she has loved and yearned for--that alone proves how important Yuu is to Haru.
And Haru's own worries about whether they could truly compete with Yuu's sister, yet determination to continue pushing ahead, sealed it. Haru is scared; but she still reaches for Yuu, and Yuu takes her cue from Haru's bravery in the face of her fears. It could be a case of being 'swept up in the moment', but really this feels like Yuu stepping up to match Haru's strength and conviction to fight for what she truly wants.
The question, is whether Haru reciprocates. Yuu has always been the more decisive of the two--she reached out to Haru in the first place, after all, and is the driving force behind their nascent music career--but Haru brings a singular passion and a warmth (in more than just her husky voice) that has pulled Yuu from her own despondency over the splitting of her family. It's clear that she thinks of Yuu as incredibly important; even as she thinks about how Yuu might still choose her over Miyuki in the event they lose this bet, she also knows how important this music they share is for Yuu, and won't accept defeeat for Yuu's sake.
I wouldn't be surprised if Haru needed a bit of time to sort out her own feelings, but she's effectively already there in all but name. I hope that whatever period of time sits between this chapter and Haru responding & reciprocating is short, but I would be surprised if Haru pulls back entirely from here. She also is fairly in tune with her own heart, and we've been trending this direction for more than a couple chapters now.
I just want to see the look on Miyuki's face when she finds out her sister's been claimed.
Thanks for the TL.