We do not know as yet anything about as to how Kawaki has got his Karma seal. But I have a strong belief that Kawaki is going to kill Urashiki Otsutsuki and get all his powers and abilities. We know that the robots Kawaki had destroyed were cold as ice.
This hints that he already has Urashiki’s powers. We saw Urashiki Otsutsuki using his technique known as the palace of the dragon king. Using which he trapped Toneri Otsutsuki in a time freeze at the palace of the dragon king for 10,000 years. And this is how we will see Urashiki Otsutsuki’s death in anime. So, while the Denki Kaminarimon novel is being adapted in anime we’ll get to see the introduction of Kawaki and Jigen much earlier than it was in Manga.