Well, it's not really a split personality. It's a possession. Vald is possessed by a demon that is a separate being. So the demon isn't part of Vald. It has just taken over his body and forced the real Vald out.
I know what you mean, but, choosing was never a conflict in the manga since Havi made it clear many many times that the one he loved was the true vald. It would make it better if you read it as the demon is just Vald's animalistic and negative tendencies were amplified (like when he was Vald but had markings, which made him more impulsive and violent) Rather than it being a completely different person. Thats why Havi calls it "beast" rather than "evil or demon vald"
Yeah I know that but you know that dream sequence Havi had with "both" Vald's wanting to have sex and he just let it happen with the demon and there was really no suppression needed. Havi does call it "beast" but he doesn't really deny it's sexual tendencies either, even when it isn't necessary.
Like I'm not really mad at Vald or the demon, but really just Havi.
I hope this will come into play in the climax. The thing is that the demon is not a beast. It is an individual being with a separate identity and genuine feelings. It is emotionally attached to Havi and Havi is--to some extent--emotionally attached to it. When the moment comes to break the curse and defeat Asterdol, Havi will face a choice. I don't think it's really in doubt that he'll choose Vald, but it will not be easy for him to let the demon go. I think it will end up being some kind of release or sacrifice on the demon's part, like the demon may sacrifice itself to save Havi.
I really fucking hate yaois with split personality characters. It's like an extreme version of indecisiveness. And the wizard dude, just CHOOSE THE MAIN CHARACTER AND NOT THE DEMON! The demon isn't him yet he still selfish, the true Vald loves you but you're still lusting for hot demon sex? Like SHIT! IM SO PISSED! Why can't we just have pure angel Vald? I really dislike demon Vald, and even though there's "hot sex" I really disliked all of it that had to deal with Demon Vald. and I know the way I described his split personality is not true to real life, but in mangas, it's inaccuracy and stupidity just pissed me off.