And lastly......(takes deep breath) spoilers. (For all you people that already know, correct any mistakes)
After the statue of pride fell, and bal masque was once again defeated. A lot of plot develops. At the end of season 2 it is thought that yuji picks shana and they all live happily ever after until some other fillers air. Wrong. (This is a theory) Yuji, instead, left Misaki City for about two months. He never met with shana, and he said no goodbyes. During this time everyone who is not crimson world aware forgets about Yuji like he dissapeared as a torch. Kazumi becomes depressed, and Keisaku plans to leave the city to join outlaw. (some other things happen, but those are the most important,I'd say) After two to three months (I forget) Yuji returns to Misaki City. The flame hazes sense a presence, but that of a tomagara. They confront this unamed force only to find out it's yuji. To everyone's shock. He has changed imensly. (mentally, physically he wore the same clothes that he was wearing when he left) Yuji, after much talking and debating, changes into his "true form"
And says his name is Snake of the Festival Sakai Yuji. He then rapes all the flame hazes (not literally of coarse) and drags shana's beaten up and bloody body to the crystal altar. There he tells Kazumi that he never felt any emotion for her and therefor sends her into a state of shock. He takes the crystal alter stating that it was his anyway.
Now to explain, inside the Reiji Meigo are two entities. There is Johan, the previous Reiji Meigo holder, and then there is Sairei No Hebi or Snake of the Festival in english. He is a VERY powerful crimson lord know as the god of creation. To stop him the flame haze sent his body over to another realm. As for his conscience, it somehow made its way into the reiji meigo. (This has not been explained yet so bare with me.)Anyway, the constant attempts of opening the reiji meigo and the constant use of spells put on it have caused Sairei no Hebi to wake up. Sometime in the second season. Yuji, then became aware of his excistance, and the two started communicating like a lord and his flame haze. The lord was present for everything Yuji did, and observed his actions carefully over this time. When the statue fell, it is presumed that Sairei no Hebi informed Yuji of his plan for a "new" world. In this plan the lord was going to create another realm where humans and denizens can live together and the need for power of excistance will not be present. Thus stoping all fighting. If this were to happen then Shana would not need to fight anymore, and Yuji and shana could live peaceful and happy lives. (theory) Yuji agreed with this idea and wanted to be a part of it. So, Snake of the festival and Sakai Yuji merged TOGETHER both physically and mentally to help better their plan. Thus creating....Snake of the Festival Sakai Yuji (play evil music with thunderstorm in the backround). After this, the new being left Misaki City and forcefully (i think) took the throne for Bal Masque. Yuji then trained his body and mind for two months and became VERY POWERFUL (keep in mind that Sairei no Hebi is as stong as Alastor is.) Now there is a giant war between the denizens (almost all of the denizens are helping Bal Masque do this plan)and the flame haze. The rest you can read into, or hasn't been explained yet.
(sighs of relief)
Any questions and I'll gladly help. Any corrections and I'll gladly fix.