Man, it's wild how many versions of the White Snake tale there are, and they all shift the focus a bit. The absolute core, though? It's Bai Suzhen (the White Snake spirit) and Xu Xian (the mortal scholar she marries). Their relationship is the whole engine of the story—her love for him defies heavenly law, and his human fear and doubt constantly test it.
Then you've got Xiao Qing (the Green Snake), who starts as Bai's loyal, fiercer sister-figure and often becomes a crucial ally or a voice of reason. And you can't forget Fa Hai, the monk. He's the primary antagonist, convinced he's saving Xu Xian's soul by destroying the 'demon' Bai Suzhen. He's the embodiment of rigid order versus their forbidden love.
Sometimes lesser-known figures like the spirit of the ginseng root who helps them get the herbs to revive Xu Xian become important in certain retellings. But the main four-person dynamic—Bai, Xu, Xiao Qing, Fa Hai—is what creates all the tension, romance, and tragedy. The recent 'Green Snake' adaptations sometimes flip it to make Xiao Qing the main emotional center, which is a fascinating take.
Basically, it's a love triangle where one corner is a moralistic monk.