Cheoksal

Once I start, I go all the way.
Jung Da-In, a national gymnastics team member from Korea's Chego High School, investigates the suicide of his childhood friend Lee Eun-Ju, caused by drugs. He uncovers a massive conspiracy tied to Eun-Ju's death. He discovers that a significant number of athletic club students are addicted to drugs that dramatically enhance performance, and have become pawns for the drug distributors. Da-In begins his relentless pursuit to uncover the truth behind Eun-Ju's death and to eradicate the source distributing these drugs within the school...
(Source: KakaoPage, translated)