@HDMI1 Only thing I can give you is the Korean Slang, "Sweet Potato" is sorta like slang for frustration/frustrating situations, eating hot sweet potatoes can give you a stuffy feeling. Shield Hero puts Naofumi in a bunch of unfortunate situations so he gets seen as a bad guy even though he's not. You feel sorry for him and that's when you say "Watching Shield Hero makes me eat Sweet Potatoes" (I feel frustrated watching Naofumi in Shield Hero).
EDIT: Added clarification.