[1] Samil was known as one of the top basketball schools outside of Seoul and he caught the attention of scouts, especially after his performances with the youth national teams.
He was named into the KBL Best 5 and nominated for the Most Valuable Player Award but lost to Busan KT Sonicboom guard Heo Hoon.
[10][11] Weeks into the 2021–21 season, Song suffered an open fracture of his left fourth finger during the away game against Daegu KOGAS Pegasus.
[12] In December, he was named Male Basketball Player of the Year at the Dong-a Sports Awards honoring domestic professional athletes across all disciplines.
[14][15] On May 16, 2022, Song enlisted for mandatory military service and was assigned to the Korea Armed Forces Athletic Corps' Sangmu basketball team.
[22][23] However, he was ultimately cut from the final 12-man squad for the World Cup as head coach Kim Sang-shik opted for a more experienced line-up.