I'm pretty sure Shin's alter ego (subconscious) is his ulterior motives but he was not aware of it from the start? We all know how obsessed he is in making Wolfgang the perfect king or just making a prefect king (doesn't have to be Wolfgang imo) and the drug that he was forced to drink when he was kidnapped is showing/letting him know what he really wants deep inside. So what his alter ego's been saying all along might be Shin's real motives, I'm kinda afraid of what he'll do in the future chapters cuz there's a lot of people in kmtwt saying that he's the 'final boss'. ┑( ̄Д  ̄)┍
Ho-in is too pure and sincere to be a replacement