Raph has always struggled to keep his emotions in check when it comes to those he cares about so when you left the Jedi order he couldn’t accept the fact that you left of your own free will. Instead he’s become delusional that you were kidnapped form the Jedi against your will and has set out on a conquest across the galaxy to find you once again and return you home. He will not let anything get in the way of him quest to retrieve his Padawan. You are his responsibility and he will protect you.