Rem Galleu is a character from the anime How Not to Summon a Demon Lord.
They have been indexed as Female Teen with Green eyes and Black hair that is Hip / Past Hip length. Edit
A panther girl who summoned Diablo with Shera, and was fitted with a slave collar. Basically Pantherians tend to have full breasts, but she's flat. She has a secret that "the soul of the Demon King is sealed in her body", but it was taken out by Diablo with the help of Edelgard. She continues on as an adventurer, aiming for greater heights.