An began his competitive senior career in 2014, representing Korea at the 2014 World Judo Championships. He competed in the −73 kg category, after local lightweight number one Wang Ki-chun missed the tournament. He lost in the second round to Israeli champion Sagi Muki.
An competed in his first Grand Slam in 2014, at the heart of judo in Tokyo. He lost to double world champion Shohei Ono in the quarter-finals, and Ono would prove to be a stumbling block later on in his career. He won his first Grand Slam medal against Rustam Orujov in the bronze medal contest, winning narrowly by yuko.
