On the other hand, I find all LIs to be dreadfully boring. The teacher's pet, the succubus with a heart of gold, the quirky manic pixie dream girl, and the sworn enemy falling for the hero are all just tiresome and uninspired. I can't bring myself to care about any of them. And Brianna? Hers is a disgusting storyline and the less I say about it, the better.
While Zero End's principal appeal definitely lies in its mysterious story and excellent worldbuilding, I find most of the characters interesting as well. I'd say Selena and Rayne are my two favorite of the assumed LIs so far.
I like Selena's intelligence, conscientiousness, and aura of mystery. I get the sense that she keeps things from Caleb (just as just about every single other character in the game does) not so much because she has an agenda but more because she is caring and worries about the consequences of revealing too much information to someone who might not need to know it just yet. Interestingly, the plot and one of the characters who definitely does have an agenda is pushing Selena directly into conflict with Caleb, but I have little doubt that she'll choose to do what she thinks is right rather than mindlessly follow authority.
Rayne offers a nice personality contrast with most of the other characters in the game, including the MC, because she is so warm and open. At the same time, her dual nature mirrors Caleb's own (which we still don't understand very well) so potentially those two -- those four?! -- could understand and relate to one another in a uniquely profound way.
I struggle with Alice and Keira a bit because in the real world there's basically no way I can imagine someone who approached me out of nowhere in a weird and even hostile way becoming immediately and seamlessly integrated into my social circle. It happens in VNs all the time, sure, but in real life I'd be actively avoiding both of them until graduation after those terrible first impressions. However, Stolen Rose wisely pivots quickly with Keira and makes her into a much more reasonable character. I think she's going to be much more than a generic tsundere -- there have already been several good scenes with her IMO. Alice on the other hand desperately still needs some more development. Right now she feels like a comic relief character who is also almost certainly going to betray Caleb in a horrible way so I'm not exactly hearing wedding bells chiming...
The Brianna storyline took me completely off-guard and I can understand why it disgusted you. I felt like there definitely needed to be more choices to let Caleb either offer to protect her without the need for sexual favors or back away from her completely. My guess is this path will either be similar to Fairy's storyline in Desert Stalker and allow Caleb to choose to try to help her heal or freely abuse her OR Brianna will turn out to have her own agenda and her submissiveness will simply turn out to have been a ploy she used to get closer to her target. At least given the state of the world in Desert Stalker it's semi-plausible to believe Fairy might actually be better off with Zaton than not, but in Zero End Brianna would almost certainly have better results if she sought professional mental help instead of relying on Caleb's magic dick if she is genuinely troubled.
On yet another hand, I like the villainous women. They are all quite entertaining. Silver, Odette and Swansong are all unimpressed with MC. They toy with him, use him and dump him. Marie is the wildcard, and her reference to MC's past suggests MC will turn the tables on them eventually. But until then, I'll keep enjoying their dynamic with our poor hero
I was actually a bit disappointed with how things went with Silver and Swansong. Silver has interested me ever since her first meeting with Caleb on the bus, but when they actually had a chance for a real conversation it was all mockery and threats from her. Caleb was perhaps too presumptuous in the way he demanded answers, but he's understandably frustrated with the way people keep fucking with his life (Silver seemingly included). As for Swansong, she seems to be a very predatory type of vampire who views humans as little more than walking blood bags...not sure there's much scope for any sort of "relationship" there, but we'll see if anything is motivating her beyond bloodlust. I wonder why Caleb's dick was out in the flashback if you accept her dance offer -- I hope she didn't sexually assault him while she had him under thrall. (There's also one scene with her I haven't unlocked yet which might be enlightening. I have so many Zero End saves that I'll likely be replaying the game for the next week or two.)
On the other hand, I did quite like Odette. She's like the vampire rocker equivalent of Quinn from BaDIK: she's horny, hates lovey dovey moments, and has evil associations. She's also a blast to spend time with and might not be all bad deep down.