Yui's endurement living with Sakamaki's/Mukami's/Tsukinami's/Kino
To understand about Yui's situation, we have to take some criterias in consideration and that her fate couldn't be changed, no matter the outcome.
So in that analysis, I will take some factors around Yui and then to the topic.
Sacrificial Bride and having Cordelia's heart
The one factor that could had being avoided, but we all know that there was one problem: Cordelia's heart. That demonic heart that doesn't alow Yui's fate to be changed, no matter what she want to do with her life
We can easly blame on two specific vampires: Richter (the one responsable to put Cordelia's heart inside of Yui's body) and Karlheinz (the masterminder of Adam and Eve project).
Living with Seiji Komori, the priest
Another factor has to be on her adoptive father, Seiji. Yui might lived alone for the most of her life, which that expains why she acts like she didn't had any role model to look up to.
Might Yui thought that she will go to live by herself and leaving anything behind her when she will be 18. Yui never exepected to be sent to Sakamaki Mansion and leaving with them. Never expecting that vampires are actualy real.
In the first game (Hunted Dark Bridal) and season 1 of anime, Yui was sent to live with Sakamaki brothers, not even knowing that they are Do-S vampires and could be cruel to her. Yui was forced to be live in this ever ending circle of constant punishments, blood drinking, harassment, insults etc.
Even in MORE, BLOOD amd season 2 shows the exact same thing happen, but is more like who is going to have Yui instead and some kidnapping stuff. If I had to say one thing that Sakamaki's and Mukami's hand in comon is that they want to became Adam, to make Yui their Eve. The second being to became more powerful and to rule Makai.
The same thing could be said even in Dark fate: another family add. In Tsukunami's case is to try to force Yui to carry many Founder children as soon as possible and even tortured her worst then other two families combinate.
Kino also shows a huge ego (similar with Ayato) and at first disrespected Yui, expecting that everyone to do for him (I'm sory but I'm not that familiar with Kino).
Yui was disrespected by those boys and yet, she treated them with kindness. The boys fall in love with her despite what they did to her makes me feel (some moments) unconfortable. If I had to chose which family could be considetate normal is imposible. Why? Because the way they treated Yui, but also they had their own trauma which let them intro that path.
Yui has her owns trauma and yet, she doesn't let that anger to comsume her and define her nature. The boys have their own trauma and pass those down to Yui, to make her suffer without an explanation is why they do this to her. Two sides in the the same coin.
I feel that hate that Yui had from fans years ago is so wrong. Just because they say "Yui is annoying" or "Yui is a pick me girl". STFU and put yourself in her shoes and then regret later for your words!
I will protect Yui until my last breath because she deserved better then those boys!
Yui did nothing wrong. She is a girl that wants to be loved. She fate was sealed since from the beganing (her birth), was neglected by Seiji, sent to Sakamaki Mansion, she endured that pain from all fronts. All because of Karlheinz's stupid exepriment