It'll be interesting to see where volume 2 takes us with the introduction of (at least one) additional character to serve as tension for these two.
Sakurako will hopefully find her footing as well, and maybe we'll get some backstory on Amano and who gave her that necklace that she clearly treasures. But I think the second volume will likely involve the third girl for the most part butting heads with Sakurako and competing for Amano's affections, with Amano playing the field on both sides and just enjoying herself while keeping other parts of her locked away.
I very much look forward to seeing whether that initial "rejection" went as Sakurako interpreted it, or if she misunderstood Amano's meaning at that time, making all this "revenge" a moot point.
But I think Volume 2 will conclude with Sakurako realizing she does indeed still like/love Amano, and feeling more and more lost with what to do about it as Amano continues to show no desire to take things to that level with her, and maybe Amano letting some of her true self slip as it pertains to whether there's a reason she's as "unattached" as she appears to be - and potentially at least one more girl being introduced (maybe that "mystery necklace gifter") during that volume's final chapter, to throw yet another wrench in the works.
But, thank you for the continued work on this, and I look forward to more.