A few hundred years ago, in the almighty Celestial Court, there are four Celestial beasts which signify four directions and elements, Seiryu, Blue dragon for East and wood element, Byako, white tiger for west and metal element, Suzaku, Vermillion Bird for South and fire element. Ganbu, the Black tortoise for North and water element. The four celestial was the guardian for the Celestial Court, their main job was guarding the center of all the elements which was in the form of a golden dragon. However, an accident happened, the golden dragon escaped from the Celestial Court to mortal's world, Seiryu and Byako were ordered by the Celestial Emperor to bring it back.
With the order from the superior, Seiryu and Byako went to the mortal's world and pretended to be the high-rank officials of M's empire, as that is where the sign of the golden dragon been seen. However, before they could found the golden dragon, something horrible happened. Due to the imbalance caused by the escaped golden dragon, dimensional break down happened in the M's empire, from normal human's eyes, it's like the sky is falling apart...
The breaking of the dimensional link caused mythical creatures and monsters leaked into the mortal world through the crack. In order to stop the dimensional breaks, Seiryu and Byako decided to get the rainbow mud from the ancient goddess in the Celestial Court, but their attempts were stopped by the Celestial Emperor, with the reason of their objective is to get back the golden dragon aura, they should not waste their time on such a 'trivia' matter at mortal's world and the Celestial Court doesn't seem to be care about that either. However, after spending some time with the people in M's Emperor, Seiryu and Byako cannot just let that mess continue as it has the potential to destroy the whole place if the crack did not getting fix as soon as possible.
---------------------------------------------------------------------------------------
Seiryu recalled a Celestial General told him there is another method to repair the sky beside of the rainbow mud, but he cannot let his partner knows, because it's too evil, that method required blood from the heart of a hundred newborn babies, so he secretly did it on his own leaving Byako oblivious. However Seiryu soon found that this method is a lie, the sky breaks apart even faster than before, that Celestial General lied to him. This whole incident had slowly drawn him away from his sanity, to make things worse he was wanted by the Celestial Court after did such an evil deed.
Knowing what happened to his friend, Byako decided to seek help from one of his old acquaintances, the Immortals who were once trying to end his life due to some stupid misunderstanding caused by the Celestial Court.
The Immortals agreed to help with the condition that both of Seiryu and Byako will need to serve them for the rest of their life and Byako agrees with the conditions.
------------------------------------------------------------------------------------
Seiryu's movement was totally sealed by the brown-haired Immortal who was trying to kill them before, while another Immortal who has long black hair and a bit frail, is having his hands fold together focusing his magic to the crack in the sky, the crack slowly closed up...
The crisis in the mortal's world had been solved, but a bigger crisis need to face by the Celestial Beast, they are now both wanted by the Celestial Court due to violation of the rule and command from Celestial Court, the biggest possibility for them was death sentence...
"Don't worry, now you belong to the Kingdom, we will not let anyone get you, including the Celestial Court." said the black-haired Immortal. Byako finally understands the reason behind the strict and unreasonable conditions they give when accepting their quest, it wasn't for keeping them under control or anything like that, it was to protect them. However, Byako knows better than anyone about the strength of the Celestial Court, so far, no one actually dares to against them in any type of form. The Immortal seems to be unaffected by that. "We have our own way of handling that... Or rather, I am the only person who can handle that." said the Black Haired Immortal. Then Byako suddenly realized that this Immortal in front of him looks quite similar to a person in the framed picture that hanged at the center of the Celestial Court...