Circle.

Japanese name: 介錯 (Kaishaku)
Members: 七戸輝正 ([[Shichinohe Terumasa]]) and 太田仁 ([[Ota Hitoshi]])
Pixiv username: seven

Kaishaku is a two-member mangaka circle, most famous for their [[Kannazuki no Miko]] creation. The circle name comes from Kaishakunin, an appointed second person whose duty is to decapitate one who commits seppuku. 
kaishaku