I never understand why so many people want poly relationships I don't like those or harems ... I'm just a person that loves a normal two person relationship...

Here you answered yourself.

I get that in here it's complicated to see a poly ending. The most realistic ending would be Mao x Yuki, and Arashi being like a wingwoman or sort of even if Yuki tells her she likes her. There should be some plot so that Yuki realizes how important Mao is for her.

But I hope for a manga with a poly ending. There are a bunch of stories with love triangle that a poly one would be a refresher. I read Canno's manga which Rin x Mayuki would have been the best ending, and I have also read Luminous Blue which needed more chapter to polish its ending.