Xyn/Zen, is a friend of Girlfriend, who was just trying to hang out with her, when her parents disapproved of them hanging out together, now she must prove she is worthy.
Xyn has brown skin and white hair. She wears a light blue hoodie, that changes to a red hoodie on Week 5. She wears a white skirt normally, but it is green on Week 5. She wears light blue shoes that change to red on Week 5. She also seems to have black sleeves and black socks. Her outfit on Week 6 is the same except she has pink shoes.
Not fully sure what her personality is entirely like, but we have a bit of dialogue from Week 6. From the dialogue, it seems she a little bit nervous around people, but mostly normal. Seems she can be a bit rude as well.
Senpai: Ah, two fair maidens have come in search of true love!
Xyn: Oh, no you've got it all wrong.
Xyn: Girlfriend is already with someone, and I'm not really the dating type...
Senpai: Not bad for an ugly worm.
Senpai: But this time you'll helplessly watch as your friend sucks me off!
Spirit: Direct contact with real humans, after being trapped in here for so long...
Spirit: and HER of all people.
Spirit: I'll make her father pay for what he's done to me and all the others,,,,
Spirit: I'll beat you and make you take my place.
Spirit: You don't mind your bodies being borrowed right? It's only fair...
Additionally, here is a file that adds her into the story mode menu.