Minor characters in High School DxD.
Golden Horned King and Silver Horned King
The Golden Horned King (金角 Kinkaku) and Silver Horned King (銀角 Ginkaku) are the legendary brother Youkai that appear in the Chinese epic novel Journey to the West. Both of them have fought against the first Monkey King Sun Wukong when he was accompanying the monk Xuanzang on a journey to retrieve Buddhist sutras from India.
Both brothers possess the Five Treasured Tools, for of which they made use of during their fight against the Vali Team: the Crimson Gourd (紅葫蘆, Kōkoro), which has the ability to suck in those who respond when their name called out; the Seven Star Sword (七星剣, Shichijōken), which has the ability to crush evil and make Youkai obey whoever wields it; the Banana Palm Fan (芭蕉扇, Bashōsen), which has the ability to create a strong wind and can send anything flying; and the Rope, which has the ability to seal ones' movements.
Retsuza (烈座) is a Youkai from the East Faction that also works for Nurarihyon. He is a Kamaitachi who resembles a human with the features of a ferret.
Kumowatari (雲辺) is another Youkai from the East Faction that also works under Nurarihyon. A lightning beast that resembles a dog and has a constantly surging lightning cloud surrounding him .
Salamander Tomita (サラマンダー・富田, Saramandā Tomita) is a Youkai who was mentioned in "The Oppai of Tennis" that lived at the swamp on the outskirts of town who usually provided Rias with info on Youkai until he moved back into his homeland when his father came down with "plate shortening disease" and to inherit his family business of cultivating cucumbers, which in turn caused him to give up on his dreams of being a rapper. His family has a rare and old Youkai way of cultivating cucumbers, so with this they would be able to pass on the traditions. Before retiring from his rapper career, his only know song was "Shirikodama Rhapsody" which Kiba often listened to and especially Koneko who was a fan of his.
Christie (クリスティ, Kurisuti) is a Gorilla-like creature under Kiyome Abe who claims to be a Yuki-onna, she appeared in "The Oppai of Tennis" Short Story. Apparently Yuki-onna being beautiful maidens was a tall tale, as they are also known as Yetis, but the freezing breath is real, Christie is also able to create duplicate clones of herself out of snow and increase her attack power by banging on her chest. She was part of Kiyome Abe's team during her tennis match against Rias. Christie has a crush on Issei after seeing him wear Honda's armor much to Issei's shock and dismay. Christie reappeared in "Issei SOS" as Issei's partner during the first match against Kiyome Abe's father, who was partnered with a Yuki-onna named Stephanie, who was also Christie's older sister. Issei lost due to Christie refusing to obey his orders and being distracted by a frozen banana created by Stephanie. She also appeared in True Volume 1 when Issei's client Morisawa requested him to summon a Yuki-onna to date only to be horrified upon seeing Christie. On a later date however, Morisawa and Christie had apparently become close friends.
Stephanie (ステファニー, Sutefanī) is a Yuki-Onna and Christie's older sister who serves under Kiyome Abe's father. She is a gorilla-like creature but much larger then Christie. She has the ability to increase her power by drumming on her chest and create ice constructs. She first appeared in the "Issei SOS" Short Story, where she was partnered with Kiyome's father against Issei and Christie, where she was able to win by creating a huge banana out of ice to distract Christie.