He was afraid that all the friendshiptrustloyalty he built with them would vanish if they learned that he lied to them and impersonated an orc. There's also the fact that he didn't want them to survive the migration to the north because orcs as neighbors is not pleasant. The conclusion is kinda funny if you re-read it. They swear loyalty and join the kingdom because they are sworn friends, believing that a curse transformed the handsome Karawichi into a hideous human. There was some other parts about how the orcs have successfully settled in the North to the point where the population is considered a breeding population, allowing new orc users to start from the northern colony as well.
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In volume 29 he uses gem sculpting to make a sculpture for a dragon. It's a quest (the dragon came and basically ordered him to make one) but Weed is pissed because he doesn't get any form of compensation - treasure, experience, anything - for it.