Oh, I understand how you feel, but I don't think it's a problem with your writing, I think that each type of yandere, as well as games, universes and so on, has its own target audience, its niche that will love it and interpret it the way you want or more than that (like me :3) I know yanderes who are worse than Louhi, there are people who defend or love, in Louhi's case I understand him on certain issues and if I were the MC (I'm already in deep shit and dying) I'd try to help him in some way, like maybe try to find out if there is a cure? Something to control the effect of his virus? Who knows! Even try to get into his head somehow so he can isolate himself forever, so yeah, the famous "i can fix him" lol
You've written him well, and if you intend to continue Louhi's saga, I'm sure that depending on the path you follow, how you develop him in the future and even the story and our choices and endings, Louhi may be seen with different eyes, or even as you wanted him to be seen, you never know. Like, I find Louhi very pushy and invasive, out of nowhere he kissed me wtf, and even bathed me, but I'm easily manipulated and I feel sorry for him because it can't be easy being a fucking parasite who just needed his fucking family to accept and love him, maybe even try to help him in some way.
The acts he commits may not be justified, but they can be understood (I think so) the worst thing is that he doesn't see or doesn't want to see that he's doing EVERYTHING wrong, but it's to be expected that Louhi has a disturbed mind (if not, he wouldn't be a yandere lmao) Anyway, I really liked everything, and I really hope I can see more of Louhi, or maybe other works, in the future <3