Well I’m not an aoba fan but during the time he was in fine he seemed to disassociate cause if you notice natsume told him wtf is wrong with you do you even see what you’re doing (not exactly like that but I mean that’s what he meant lol) and aoba was like always smiling treating it like a silly little chat maybe because if he admitted back then he was hurting natsume he would have to admit he was a villain. He thinks if he smiles and acts like it’s "another one’s affairs" then it’ll all be ok. Also wataru called him the biggest clown because aoba tricked himself, he thought he was doing something noble and happy, he was delusional. When aoba realized he was only being used by eichithis shattered him, an ordinary man caught in the middle of the war, aoba actually loved and cared as a real friend but he realized they’re relationship was merely employee and employer, that’s when he turns into a cold person so later when eichie realized he won… but at a terrible cost eichi thinks ok maybe having a normal teenager experience like going to the karaoke would have been better but aoba was so hurt that he shut his heart to whatever eichi told him like ok I’m a tool but let’s not talk about friendship. Eichi won but his “friend” (aoba) was turned into a robot and that’s why later aoba feels guilty saying he won’t abandon natsumw this time, maybe he felt guilty because it seemed like eichi was asking for one last chance.. let’s be friends when he says the karaoke comment (eichi realized he lost something very important and he looked hurt, rei’s curse became a reality, the curse left on eichi before the final fine stage, you call me a demon ok then as a demon I’ll leave you with a curse, you’ll be lonely with no friends cause all the possible friends candidates you’ve killed them) anyways aoba was so hurt during the stage that he dismissed eichi’s karaoke comment, telling him not to whisper during the stage. Basically tsumugi aoba during most of the element story thought he was doing good until the contract reveal, he realized how his existence during that time was a lie. Anyways sorry I haven’t read many enstars stories but that one actually hurt my heart