Raphtalia

Raphtalia is a Tanuki-type Demi-Human who was the first real member of the Shield Hero's party after he purchased her as a slave.

She has undergone some significant changes throughout the story. When Raphtalia is first introduced, she is a child that has long, unmanaged hair and a dirty cloth gown. After being purchased by Naofumi, he gave her a haircut to an acceptable length, gave her a bath, and bought her a much more suitable set of clothes to adventure in.

After several weeks of traveling with Naofumi, Raphtalia's body inexplicably changes and she gained the appearance of a teenager or young adult. It is revealed that demi-humans grow in relation to the progression of their levels, which led to Raphtalia's rapid development.

[Spoiler] Raphtalia later obtain one of the eight vassal weapons from another world granting her the title of Vassal Weapon Wielder and Katana Hero. Due to the passive effects of the Vassal Weapons her slave curse seal was removed. [/Spoiler]

(Source: The Rising of the Shield Hero Wiki)