How thrilling would it be if your grumpy ex-boss becomes your new junior intern? Old School Intern is a funny office drama about Ka Yul Chan (Park Hae Jin) who quits his job after not being recognised for his innovative ideas from his old school boss. Soon after he lands a new job where he becomes the head of sales and marketing. To his thrill, he gets a new intern who happens to be his ex-boss. Will this be an opportunity to take revenge or will they grow fond of eachother with growing time?