A highly acclaimed general from Tai, Asen and Gyousou were believed to be the kingdom's strongest military commanders. When Gyousou became king, he continued to trust Asen as though he were a brother. He accompanies Taiki on a diplomatic visit to Ren and is seen as an amiable and trustworthy person.
However, at some point as Gyousou began to purge the court of Tai of its corrupt influences, Asen grievously betrayed the king, who went missing shortly afterward, and usurped the throne. Asen cut off Taiki's horn, an experience that was so traumatizing that Taiki disappeared to Hourai. Asen's motivations for betraying Gyousou is unknown, though it appears that he has justified his actions with the belief that the mandate of heaven applies only to the ruler of a country, proven by the fact that heaven has not interfered with he has done to Tai.
With Asen in charge of the kingdom, Tai has been ravaged by civil war and is on the brink of destruction. As General Risai's attempts to fight back fall apart each time she attempts to build up a counter force, the country is locked down and none of its citizens appear to be able to leave. Risai eventually escapes with great risk and terrible injuries to Kei, where she beseeches the new monarch of Kei, Youko Nakajima, to aid in locating Taiki.