[X] write-in: Comforting. Kana is nervous and likely picking up a lot of everyone right now while Utau has gone very prickly. You want to calm them down, reassure them, ground them... luckily all three of you are telepaths here, so you can just skip over fumbling with words and go straight to mind-hugs and grounding.
[X] Write-in apologize for taking awhile. If Utau does seem to have overheard something and wants to talk about it right away... then and only then ask if it can't be discussed after the Birthday party, as this wouldn't really be the best moment. Discuss with Akane telepathically as needed beforehand on what can and can not be said to Utau, you did promise to let her ok such things after all. Though try to convince her in case Utau did overhear that perhaps you should tell her at least a bit of what's going on sooner rather then later, she'd probably find out somehow otherwise anyway.