Shinkawa was one of the top members in the red guild «Laughing Coffin». He was a master of the «Estoc Thorn Sword» that was bathed in the color of red. He holds a grudge against Kirito and the clearers that defeated Laughing Coffin in the anti-PK raid. He was also partners with Johnny Black, and together served as a combination where they poisoned and killed.

(Source: SAO Wiki)