One of the Hachiyō, he is the Genbu of Heaven. Eisen is the Emperor's half-brother who has left the Imperial Family and become a monk

Akane Motomiya and her friends Tenma and Shimon are pulled by a demon into another world, where Akane becomes the Priestess of the Dragon God. The people of this world tell her that she is the only one who can stop the demons from taking over; meanwhile, the demons want to use her power for their own ends. Luckily, Akane has the Hachiyou, eight men with powers of their own who are sworn to protect the Dragon Priestess. 
(Source: Anime News Network)

One rainy day, Akane crosses path with a kind young man who tacitly offers to her his coat. On their second encounter, he confesses that he has no recollection of who he is, his name or his past, but feels contented by just being with her. Besotted, Akane sets out to find his name, and to unravel his enigmatic connection with a famous cursed dance rumoured to kill anyone who attempts to perform it.
 
(Source: Anime News Network)

The plot revolves around an ordinary high school girl, Akane, who is mysteriously transported back in time to the Heian period of ancient Japan. Kyou, now known as Kyoto. Akane discovers she has been pre-ordained as the Ryuujin no Miko (Priestess of the Dragon God). However, the purpose of her transportation to the past is clouded by the involvement of Akram, the head of the Oni Clan, which has sworn death and destruction on Kyou. Akane is therefore appointed eight male protectors, the Hachiyou (Eight Leaves), to stand by her side and guard her from the danger that awaits... 
(Source: Viz Media)
 
Included one-shots: 
Volume 1: Love-X 
Volume 4: My Mind, His Mind

Whisked away to the land of Kyou, Akane learns that she is the Ryuujin no Miko, and meets the Hachiyou, her protectors. They must defeat Akuram, a demon who wants to destroy Kyou using the power of Azusa, a woman who has the power to absorb human energy. If Akane and the Hachiyou cannot defeat Akuram and bring peace to Kyou, Azusa'a power will destroy the humans. 
(Source: Anime News Network)