Hey so I reread the description after writing this monster comment and it does in fact say that Sena's feelings towards Yuuna are romantic so this makes everything I just typed obsolete. Nevertheless, I still think the way relationships are portrayed is really profound and this series is incredible to me. I'm not deleting all this bc I put in a lot of effort and thought into it (even if it ended up being for naught), so maybe someone will read it. Maybe not. Idk I just have a lot of thoughts
Reread this series and God do I love it
I remember being super apprehensive because of the incest tag, but I think Sena's feelings towards Yuuna is more profound than that
What we know from what was explicitly said is that Kiku is in love with and loved Sena, Kiku was never in love with Yuuna but sees her as a friend and someone like family, Sena loves Yuuna, and Yuuna cares deeply for Kiku but was never in love with her. The word love is used multiple times, but it's never truly described.
I'm starting to lose my train of thought, but what I'm trying to say is that Sena viewed her feelings towards her sister as "dirty" and "unnecessary," "selfish" emotions that have her "dripping with muck." Despite that, despite saying she loves her sister, nobody ever puts a name to it. One could say it's implied that it's romantic, implied to be incestuous, and I understand that viewpoint, but I think it's also important to consider that Yuuna and Sena were each other's only family. Sena relied on Yuuna because that was what Yuuna wanted. That they were each other's only family was why Yuuna started dating Kiku in the first place; she wanted to have a family, and deep down she wanted to rely on someone too (it's the older sister syndrome y'all).
Losing my train of thought again. It was a very intimate relationship between Sena and Yuuna by virtue of how important they were to each other. This is why I'm apprehensive to say the story really does involve incest, and why I think it's so poignant. I think the muddiness is so imperative in its narrative. Delving into anything more explicit, putting a name to Sena's feelings for her sister, would only discount their relationship and what they undoubtedly mean to each other.
(P.S. man this aged poorly ← me now after rereading the story description. Sighs)