Sothis

"Well then, it's up to me to guide you from now on, right?"

- Sothis talking to the Byleth

Sothis is a character from Fire Emblem: Three Houses. She is a mysterious girl that only Byleth can communicate with.

Etymology
Sothis is the Greek name of the Egyptian goddess, Sopdet, who is the personification of the star, Sirius.