Keenan is a soldier of Shin Makoku and subordinate of Günter. He is a master archer who is able shoot anything he aims at. 

Yuri Shibuya was living a pretty normal life. That changed the day he was dunked into a toilet after an attempt to save a classmate from a gang of bullies. Instead of just getting a good soaking, he's pulled in. The next thing he knows, he's in a world that vaguely resembles medieval Europe. If that's not odd enough, he's told that he is to be the next Maoh, just because he has black hair and black eyes. The Maoh is the King of the Mazoku, who are coexisting not-so-peacefully with the humans in this world. Much to his subjects' dismay, he's totally different from the rulers they're accustomed to. He's kind, considerate, a believer in justice, and not willing to use violence to solve conflicts. Not exactly someone they want running a country on the very brink of war. Now, Yuri has to deal with trying to become a good Maoh, while at the same time attempting to adapt to this lands' customs and culture, all in a world where the tension between the humans and Mazoku is reaching its peak.
 
(Source: Anime News Network)

[Wiki (jp)](https://ja.wikipedia.org/wiki/西村朋紘) | [Wiki (en)](https://en.wikipedia.org/wiki/Tomohiro_Nishimura)

At the end of season 2. Yuuri defeats Shinou, but since Shinou had been defeated, Yuuri and Murata could no longer go to the Shin Makoku. However, because Yuuri had fought and defeated him, his powers had surpassed that of Shinou's, resulting in him being able to rely on his own power to return to Shin Makoku. 
After the ceremony at the age of 16, Yuuri slowly begins to discover that much has happened while he was away. The ten officials of the noble family have decided to make Wolfram the next Maou, but now that Yuuri has returned and taken back his role as Maou, complications arise when one noble disagrees with Yuuri returning to the throne. 
In addition, an ancient secret society that threatens the peace of both humans and Mazoku has risen, and a fight for the throne that now leaves the nobles wondering who is the legitimate Maou.