Class of Lies
미스터 기간제 (original)
Ki Moo-Hyeok, a lawyer with a high winning rate, only cares about money. Due to a murder case at a high school which he deals with, his reputation as a lawyer hits rock bottom. To regain his good name as a lawyer, he sneaks into the high school and work as a temporary teacher. He tries to reveal a secret which the students have, and gets involved with Teacher Ha So-Hyun, a P.E. teacher who loves her students. They then face the students'secret.
Starring Yoon Kyun-sang, Lee Jun-young, Geum Sae-rok, Choi Yu-hwa, Choi Kyu-jin, Jang Dong-ju, Jeong Da-eun, Byung Hun, Kwon So-hyun, Jun Suk-ho
Watch "Class of Lies" on Rakuten Viki released in 2019. It's a crime and mystery show, and has a rating of 7.8 out of 10 from Imdb which is usually fine for this kind of show, and is currently available to watch for free.