Sakujun Sa

The middle brother. He finds the world very boring and seeks to amuse himself, morals are of no consequence. Upon being told by his grandfather that he is to marry the Kou princess, Sakujun arranges to meet Shuurei in person, under the disguised name of Lin Senya, and finds himself intrigued by her.

[Spoiler] He dies right before season 1 ends. He also shows himself to Eigetsu in season 2 for the first few episodes as a ghost, and also as part of Shuurei's flashback. [/Spoiler]

[Spoiler] Even though he is told to be seeking amusement from her until he gets bored, he slowly falls in love with her.He said in the game with Seiran that will give her anything she wants and will do anything in his power to satisfy her and that the only thing/person in the world that matters to him is only Shuurei. In his last moments when he's about to die he again comments on how he liked Shuurei with her hair down. In his mind he said that in the games he played so far Shuurei is the only one who has the ability to easily beat him while he had to struggle. Then when he asked Shuurei to give him Gok-Long tea he puts poison in the water and antidote in the Gok-Long flower. In the end, she still didn't pour him the Gok-Long tea causing him to die, and in his very last word he said Shuurei. (He never called her by her name.) [/Spoiler]

(Source: Wikipedia, edited)