Luka kinda gaslighted amnesiac Ivan into their relationship. Part of Ivan knows something is wrong but he is starved for any positive human relationship. And Luka is the closest to it he could have in this time. Ivan knows he is being manipulated but he accepts the manipulation
Mizi and Till hates Luka for the memories they had in their previous life. Where he used Sua's and Ivan's death against them. They hate him more after seeing Ivan (he looks smaller than the Ivan in their past memories). They believe that Luka is manipulating Ivan. They're not exactly wrong.
Till also misses Ivan in all ways that matter. He did a lot of contemplation in the rebel base and the memories he loved to remember where those with Ivan. He also wants to know what Ivan truly feels regarding Till after the memories of the kisses and sacrifice. Which is why it's hard to see the current Ivan glued to Luka the way Ivan used to do with Till. Luka keeps smirking at his direction and Till wants to punch him but hesitates because Ivan would glare at him for daring to hurt Luka-hyung. (But at the same time Ivan will bonk Luka's head and tell him to stop antagonizing others and Luka will just pout and then Ivan will pepper his head with kisses) Till is jealous
Ivan doesn't like going near Mizi, Sua and Till. While there's a tiny part of happiness that Ivan didn't understand, the larger part of him wants to avoid them. It's not just because of Luka, Ivan gets headaches everytime he spends too much time with them. This Ivan doesn't like pain because Unsha and even Luka ingrained it to him.
Till and Mizi definitely wants to cry seeing Ivan avoid them. Sua feels strange at that. On one hand, she had always wished that Ivan go away. However, it was strange to see Ivan not even wearing a mask of humanity in interacting with them. Mizi had given Sua an equivalent of verbal beating so Sua did a lot of reflecting. She will admit that she had been unfair to Ivan in both lifetimes when Sua had also depended on him for a reality check and she can't even apologize for her wrongs when Ivan doesn't remember.
Hyuna kinda pities him for being the object of Luka's obsession.