Mukai Kohinata

was a Konohagakure jōnin and Anbu who came from a family that was distantly related to the Hyūga clan. It was soon realised that Mukai also was a suspected spy for Kirigakure.

Itachi Shinden: Book of Bright Light
Danzō Shimura had ordered for one of Mukai's team-mates injured so Itachi could be the "fill-in" for the team. Their mission was to spy on Kiri and Sunagakure shinobi as they were appearing to be forming an alliance. Before the mission, however, Mukai went out drinking and smoking and compromised the mission. While being chased by the Suna shinobi, Mukai revealed he actually had the ability to awaken the Byakugan in his left eye and defeated the twenty shinobi.

Personality
Mukai was a smoker as well as an alcoholic and would indulge in these vices even before important missions.

Byakugan
Being distantly related to the Hyūga clan, Mukai was able to find a way to activate the Byakugan in his left eye as a genetic throwback.

Taijutsu
Mukai was hailed as a taijutsu expert appearing to use a variation of Gentle Fist.

Trivia

 * literally means "small sunny place" and "mukai", when written as "向い", means "facing".
 * Reversing the kanji of, one gets 向日, which can be read as "mukai".