"Oh?! Whyyyyyyyyy!!! Why did I suddenly become a small anchovy?!" Majoring in Food and Nutrition, holding a Level 1 qualification as a life sports instructor, and the ultimate gym enthusiast, Yeongjik! That's how he was... until one morning, he woke up in the body of Sejo, the second son of King Sejong, without all those bountiful muscles.

Yeongjik goes to meet the King Sejong, who may or may not be his father, and can't contain his excitement at the thought of meeting this great king in person. Huh? King Sejong...😕 Wait, is that the morbidly obese man who seems to struggle to breathe? King Sejong with apparent diabetes... Ailing officials with chronic diseases... 15-year veteran fitness trainer Yeongjik, the pride of the gym enthusiasts, begins to burn with determination. "Well, shall we try spreading fitness and working out in Joseon for once?!"