Ehh? I didn't realize Alice's love interest imagination was that good.
Mine is a lot more... amorphous...
I create a lot of stories in my head. Most are slice of life or romance~
... And most I won't ever write.
The one I'm currently working on has a MC that had a girlfriend, broke up with her, got another girlfriend and married her.
Meanwhile, the MC's little sister is engaged to two different girls and is in love with a 3rd one, though she doesn't want to pursue a relationship with the 3rd girl, as she is happy with her fiancees~
... So yeah, I guess!? I imagine love interests with some ease! xD
... I do have a harder time imagining male love interests though, it's easier for me to imagine female love interests, so the stories often turn yuri~
I dunno, I'm just bad with depicting men in general when creating stuff~
I've never read too, mostly snippets of plot and all~
But it's kind of different from what I gather, since there isn't a 'fixed' protagonist and each volume focuses on a character and their struggles.
I checked a bit just now and apparently it's actually supposed to be an equivalent of Fate Zero instead of F/SN... Which is a bit of a bummer.
Didn't know this thing about changing protagonists though... You sure you aren't talking about Fate/Strange Fake instead of Fate/Prototype: Fragments of Blue Silver?