it's going to be Olivia.
She is the one who already integrated into Machino's world and Sofia is going to return.
it's the underlying message here.
also, no harem ending.
I wholeheartedly agree. I feel the author has been laying the groundwork for this the entire time. Olivia adapted to this world
on her own. Found a job, secured residency, attuned herself to customs and rules that are essentially the polar opposite of everything she knew in Celestia.
It's been heavily hinted that Night of the Shooting Stars will send everyone back to Celestia. This is just my own headcannon but I think as the Princess, Sofia will be sent back to assume the throne. But Olivia, through "the power of love" or some equivalent narrative device, stays behind.
I think in this kind of story, you need a winner. Setting aside that Machino has already effectively "rejected" Aurora, Luna, and Carla—and Olivia straight-up said she'd only go on this date if Machino chose between her and Sofia, structurally, a harem ending wouldn't work for me.
Reason being that Machino's been spiraling over not making a choice, realizing that avoiding it only hurts everyone more. She's built genuine, deep relationships with each of them individually. So forcing them all to "share" would undo the emotional weight the author spent all that time building. And honestly, the story carries somber undertones with Machino having lost her parents, I don't think the author's afraid to let the other girls go. One writing structure I like is when an author recycles something from earlier in the story but puts a twist on it. Instead of losing her parents again, I think sending the other girls back will hit that same emotional note. Though, this time, Machino won't end up alone finally have an unbreakable bond with someone who won't leave her be it Sofia or Olivia.
May the best girl win!
Thanks for the translation!