Sage is Forbesii's maid. In the standard timeline, she marries him and is Nerine's mother.
Sage is very energetic and cheerful in almost all circumstances. She is an excellent housemaker and good at hiding her feeling, especially towards Forbesii, to whom her whole heart is dedicated. However, since Forbesii is a prince and she is just his maid, Sage tries to provide services to Forbesii and devotes her life to it in the hope that she may not have to leave him when he ties the knot with his fiancee, Ai.
(spoiler hidden)[Edited from
Wikipedia]