First Season - Ahiru is running the show hands down. As the best character but also all of the plot device and everything the show revolves around.
Second Season - Fakia/Fakir seems to come in as the co-star along with Ahiru. He still gets second billing and the show revolves around Ahiru, but he almost forces his way out of his 'part' in the story and damn he has some good parts in the plot. Sure changed from his arrogant 'fuck you, don't touch my Mute/Mytho' in the first half of the first season.