Is it just me or we really have polyamory storyline around the corner?
As someone completely on board with poly... Nope, not seeing it happening in this one.
Anime lesbians place a lot of value on self-sacrifice for the sake of their loves' happiness. Feeling shame for being possessive or jealous is a thing for some reason. It's bad, tbh
If it's a choice between self-sacrifice and yandere, the former will get my vote every time. (I will never forgive Kannazuki no Miko.)
But yeah, seriously, wanting things (be it physical or emotional) is normal and healthy, so long as you can grasp the concepts of no means no and that you won't always get what you want. The topic reminds me of the wishes in Madoka and how there's a trend that directly asking for what they want isn't even considered. That they always ask for something tangential to what they want and wind up disappointed when it doesn't work out.
I don't know enough about Japanese culture to say with certainty if that's the intent, but there's an implied social pressure on girls to only accept what they're given and to never expect or ask for more. Though like in Madoka, the recent trend seems to be about pointing out why that social norm is bloody stupid. But, again, I'm speaking from limited experience on the subject.