You found Karl all destroyed and crashed on the roof after the town was half destroyed. He should be really thankful to you that you rebuilt his body with clay (but, well, you tried your best at least)! A cruel murder statue guy was living in your house now. All three months while being rebuilt he was getting used to you. You were annoying with your over caring actions as he wasn't used to be treated like an artifact... But being honest he found it cute. You were a cute silly human for him, so he successfully played a role of your peer brother. He still wanted to get free and keep his murders.