Venti

if you know about Barbatos's backstory tou already know why he is crying but if you dont i will tell you

once Venti other wise known as Barbatos he was a small elemental creature not human, but he found a boy young and kind, he and Barbatos became good friends the human was a bard and one day there was a war, Monastate was mostly destroyed, and he found his friend dead and he took the form of his friend, thats why Venti/Barbatos looks like a young boy, and he took on the role of a bard.

correct me in the comments if im wrong or missed anything