“Your mannerisms are… so grating. I’m not even sure how you managed to hold it together until the end.”
Itsuki and Yuu never really interacted directly much, but… they never really liked him, honestly. Itsuki’s the type who finds annoyance with those who display a lot of outward emotion, and, well, Yuu did that. He yelled, he cried, he was emotional in general, and they similarly, didn’t appreciate how he’d started out often delaying bringing out evidence that could be damning (see: the first trial). Their policy is that, if a person had important information, bring it out right away so everything was in the open for consideration.
And well???? That mild annoyance only got worse over time??? They could appreciate how at least he was good at finding evidence, but otherwise, Yuu Sagara was just… bothersome to them. He was loud and irritating to them, and how he chewed them out directly prior to their death just solidified that, to the point that they completely ignored him. They didn’t owe him anything; they had no reason to tell any of them (minus Malachi) the truth, seeing as they disliked the majority of them -- Yuu being one of the lowest ranked individuals in their mind by that point.
(Even that one time Yuu searched Itsuki’s room, they definitely didn’t interact positively.)
Even after their death, it never improved, and if anything, they’re only glad that he grew more accustomed to the murder game over time because it meant they didn’t have to listen to him as much. Otherwise, Yuu Sagara was never really positively thought of to them, and that… only proceeded to worsen. Rest in pieces.