User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-16281343-20150310114346/@comment-73.178.133.185-20150310163254

This refers to the Five Great Head Clans/Families that are the focus of the web novel Slashdog. The "inheritors" Jop talks about are the strongest of each of these five clans and are given the names and powers of ther clans' guardian sacred beast (Kushihashi Seiryuu, Doumon Genbu, Shinra Byakko, Himejima Suzaku and Nakiri Ouruu). The Sacred Beasts originate from the Chinese Four Symbols (Qinglong/Azure Dragon, Xuanwu/Black Warrior*, Baihu/White Tiger), Zhuque/Vermillion Bird) which are each given one of the Chinese Five Elements (wood, water, metal, fire, earth) with the Yellow Dragon (Huanglong) being the additional fifth. Each is considered the guardian of a specific direction: Qinglong/Seiryuu of the East, Xuanwu/Genbu of the North (a tortoise with snake tailss), Baihu/Byakko of the West, Zhuque/Suzaku the South, and Huanglong/Ouryuu of the Center. Generally speaking, the Yellow Dragon is usually depicted as being the strongest Sacred Beast and has links with the Chinese Emeror.

In universe, not much has been revealed about the Sacred Beasts themselves. However, it was due to the Himejima clan's fear of losing the protection of Suzaku due to the relationship between Shuri and Baraqiel, and the birth of Akeno, that led to Shuri's death and Akeno's exile. As for the clans themselves, other than the fact that they adhere to Japanese esoteric/religious traditions, such as Shintoism and Omyoudou, it has been revealed that the Nakiri clan is considered the strongest and serves as the mediator between the other four, thus Nakiri Ouryuu is a rather important figure amongst the Five Great Head Clans. (The fact that Nakiri has appeared at Kuou Academy and even joined the Student Council suggests that they Clans have possibly joined or are thinking of joining the Alliance).