Vixen

"Oh! There's not much resemblance between you brothers, is there?"

- Vixen

The Vixen was a female demon who associated with the eldest Thunder Brother, Hiten. Hiten thought that she was very beautiful and kept her for company. However, he did not value her life and killed her with a lightning blast after getting angry at his brother, Manten.

Anime Vs. Manga
In the Anime, the vixen is killed by Hiten. She is electrocuted to death after Hiten finds out that Manten hadn't obtained the Shikon no Tama shard from Inuyasha. In the manga, she is also killed by Hiten for the same reasons, except he punches her through the head, instead of electrocuting her.