[ he'd told jinx, because he'd heard her name as powder and how drastically she'd reacted to it--at that moment of weakness, he wanted to exchange his even to a mortal girl in some attempt of equality.

he'd told clarke, because she seemed intent on challenging the captain and if the captain might threaten her (remembering that rita had lost her hand) he wanted to help her.

he hadn't told mizuki. part of it is timing. part of it is knowing mizuki's race's history with that seaborn god in his world... even when mizuki deduced he was a god he never quite seemed curious about it, unlike clarke or jinx. and venti was perfectly happy to simply continue as he was, a mundane if windborne bard. he'd never really showed off his status as god. he'd shown up only a few times as barbatos in mondstadt's history. it wasn't something he flaunted. there was a lot about his godhood he didn't exactly keep hidden but just wouldn't quite come up, there are aspects of his history he would keep unsaid even from lumine-- ]

It's Barbatos. [ as he quietly links his hand with mizuki's, a soft squeeze. his voice and eyes lowered. the name of a demon in another world. ] Miss Friday doesn't know my name, I assume the Captain doesn't either. If you need me and the wind may catch my name, I'll fly to you.

[ he's not exactly like xiao, he wouldn't come at a call. he hears prayers. he doesn't answer all of them or even a lot of them, he believes in humanity over gods. but in the absence of prayer he might catch every invocation of his name in this realm.

and there's also this--when his identity was this questionable he would quietly prefer his life as venti, a bard, than barbatos the absent god. ]