well, Umi should have been a little more talktive for sure.
But I don’t think that Itsuki has bad intentions: probably he experienced something that didn’t change (maybe something in which he made an effort too) and it was an awful situation, so he never reserched further and thinks that the future he sees can’t change if drastic decisions aren’t made.
Also the fact that she's going to hide information about Itsuki's vision is just asking for more forced drama down the line.