Muratake is one of the four virtues that serves the White and Blue Kings. He eldest of the four and specializes in medicine and healing.

Spoiler

Unlike the other virtues, Muratake is loyal to Asagi first, and Ginko second. This is probably because he raised Asagi since he was a baby. In the epilogue chapters, Muratake is shown to be traveling with Asagi, and unfortunately having to clean up after him. (source: soaring_wings)