I can't help but see skull enema and I wonder how that works.
Well, seeing as a human rectum can stretch far enough to accomodate at least one racoon, it'll probably be something a lot like that. Though with a whole lot less fur and angry wiggling.
She is a white snake girl, based on a recurring theme in Japanese folklore rather than any particular species. White snakes are commonly believed to bring good luck, so in other words, she's introducing good luck for the year of the snake.
Sancho, I have conceived an idea most ingenious. We shall all archive artwork created by humans, to learn their customs. We shall sate our hunger by the sheer power of appealing anime iconography, and then recreate those scenes!
Uh, given this artist's other works, are we sure this isn't Hajime Shino? And therefore a boy, not a girl? Someone might want to check that out. It certainly looks like him.