it wasn't really sudden. its about 5-6 years later since they became working adults from second year students. and his love for eating shifted to arai instead c:
Also since he is now a working adult he probably to busy and running around also he said that he is not that much of a foodie anymore... Also let's be honest while growing older It's best to bring your weight down to a "normal" range so that you will lessen health risks such as diabetes, heart attack etc. I mean I am 80 kg myself (like the character) and though I am quite tall (so I don't look as chubby) I am still trying to lose and stop being overweight...
Cute, but rlly not happy abt how he all of a sudden got super skinny.