Decided to do one too, was pretty fun. As for the tiers:
Top tier means I consider them great in personality, looks and scenes that they have. Except for two, all of them are rather physically imposing, kinda my type, personalities are more varied, having rougher ones like Beris and Kaia but also the gentle ones like Minori and Tabitha, and some in between.
Tier below that means I still really like them, just not as much as the top tier.
Fuckbuddy tier means I am not super excited for one reason or another, I can enjoy a scene with them but it is nothing to write home about at the moment, some select few of them could move up the ladder with CGs or new good scene or two, maybe, but most are stuck here for good.
The blue tier means that I am inclined to like them and put them into one of the two top tiers, but there is at least one big problem that disqualifies them entirely. Kotone is a complete cunt personality wise, Jora and Amy have adorable personalities but just look way too monstrous for my taste, Feng is a corpse and I prefer my meat unspoiled, etc.
Not interested tier means just that, no interest really, slimes, ghosts, weird plants, they all don't do anything for me but they don't quite disgust me.
Starved for content should be obvious, either no or too few scenes to really judge, which is particularly shameful for Amber as she is not only one of the oldest characters, but also has the kind of personality and position in the city that should accumulate scenes very naturally as you progress through the game, yet like the others she is kinda limited to her role only.
Last tier are the only girls that actually disgust me when I picture scenes with them in my head. Massive fuck off spider, massive fuck off lamia monster, they are like Jora but without the massive personality bonus. Worst of all is Gren who, pardon me for even speaking it out, is french, thats an instant no no.
