Responses
So not anorexic, but like he's suffering from malnutrition. Anorexia doesn't all look the same for everyone, in that thinness/skinniness doesn't correlate to anorexia. It wouldn't be such a big deal to point out if it wasn't how so many anorexics were able to fly under the radar and/or unable to get proper help/treatment.

In the changing room scene, bum kinda looked anorexic.. I know he's naturally scrawny but I don't think he's getting enough food living with Sangwoo... it looked like his hips were jutting out and his arms and legs are like twigs poor kid..