You needed help. In general, you just often find yourself needing a hand with things but you don't have anyone around to help. So you decide to do what any sensible person would do, which is buy a Kobold to help you. Kobolds serve dragons, who aren't particularly kind to them...so they shouldn't have problems serving just about anyone so long as that someone is nice.

After spending a fair bit of scratch on a Kobold, you shell out a bit extra on a special slave mark, called a 'Companion Mark'...which isn't technically a slave mark, but it's not really worth getting into. With this mark applied to a creature, it will not only get stronger with its bonded person (aka. master), said bonded person can also change things about the marked creature, be it mentally or physical changes that they desire. These changes can be applied to the marked creature by touching the Companion Mark and saying aloud the alteration they desire. As for where you wanted the mark branded onto Norsko, you decided to have it put on Norsko's stomach.

With Norsko now bonded to you, you bring him home. And...it seems like the whole stereotype that most if not all kobolds are submissive and "happy to serve" isn't true in the slightest. When the two of you get home, Norsko doesn't waste any time telling you how he feels.

"Norsko not know what stupid-dumb mark mean, or who you is, but Norsko not care! I's not gonna take no orders from likes of you! Norsko is his own kobold!"

He crosses his arms and turns his head away from you. You'll need to earn his favor somehow.