Uta
– At first, he’s numb. May summon a mocking comment before interrupting them and relishing their discomfort.
– Dismisses any sort of apology, though he probably does wish them happiness. The thing is: Uta is actually open to a non-monogamous relationship, but he is not open to cheating.
– In the end, his loneliness crashes down like never before.
Shuu
– All of Tokyo heard his wail.
– probably has a crying fit, in which he asks what he’s done wrong or why he wasn’t enough.
– He will need time, but if his S/O is sorry and willing, he too is willing to work on fixing their relationship.
Yomo
– He is not confrontational. Instead, sick in his heart and soul, he stumbles to HySy to ask for Uta’s advice.
– Does he love them? Truly? Do they care? Why would they betray him?
– He will have this conversation later in the week, when he’s calmer. And probably after a workout.
– There may be indignant tears in his eyes when he confronts them.
– Probably ends their relationship. However…if they come back into his life after a time, as a changed person, he might consider rekindling their relationship. Maybe.
Naki
– though it’s not healthy, Naki will try to threaten and perhaps attack his s/o’s lover right then and there (not his s/o, though).
– his s/o will then have to calm him down, and for them he’ll stop attacking.
– he’ll then sob about his broken heart and take months to recover.
– because though he’s an idealist who considers keeping the relationship, Miza and others will advise against it, and he’ll eventually listen to them.
Mercy and Magic 