The Merchant's Guild (全商連 Zenshōren) is an association for merchants in Saiunkoku. They were first seen during the Sa Province Governors Arc.
The Kou clan handed over the right of creating seven coloured luminous paint to this guild in order to get their assistance to Kou Shuurei, who was supposed to be the new governor of Sa Province.
Sai Shou (柴 彰 Sai Shō) is the Branch Head of the Merchant's Guild in Kinka.
Sai Rin (柴 凛 Sai Rin) is the former Provincial Head of the Merchant's Guild in Koren.
Kaku (カク Kaku) is the person Kou Shuurei believed was the Branch Head of the Merchant's Guild in Kinka.