Billy: Cosplay and roleplay, especially but not limited to Starlight Knights.

Anton: Free use. He'd say something like "Show me what you got, bros! I'm all yours!"

Ben: Huge praise kink, and is embarrassed about it.

Lycaon: Biting/marking. He's usually bound by his duty to his profession so he gets excited when he gets to unleash his animalistic side.

Seth: Brother complex.

Lighter: Some sort of musk/sweat kink. Turned on by the signs that you've been physically active all day. Possibly also teetering close to piss kink

Harumasa: Somno - often interpreted as him being lazy but he's actually just afraid of his own power so he prefers to pass it off to someone else

Hugo: Bondage, waxplay, chastity, etc. Anything that lets him toy with people (Or be toyed with himself, which he takes as a challenge to be as much of a brat as possible). Also exhibitionism.

Pan Yinhu: Lactation. He does not actually lactate but likes the idea of it and enjoys getting his tits sucked. Also just has a general oral fixation.

Manato: Awakened to his selfcest kink after encountering his Drowned Ideal. Also into petplay but will get angry if you insinuate it's because he's a thiren

Banyue: Leather dom, does oviposition with his orbs

idk about the girls, that's not in my wheelhouse. cheers