Sayu is a ghost that lives in the physical plane for a long time. Eri's grandpa was a sage that protected her since she's a "catalyst" for evil spirits. After he passed away, Eri started taking care of her and eventually they started dating.
Sayu started using the internet to get in touch with Eri and the modern world so she just starts saying random shit she sees online to mess with Eri.

https://x.com/SquishLewds/
https://bsky.app/profile/squishlewds.bsky.social
https://www.patreon.com/squishlewds

her gyatt is plappy

Base +7, kikimaru024 +30, skenver +6