B2ST's Junhyung, BTOB, and Ha Yeon Soo have collaborated to reveal a special song for the viewers of their drama 'Monstar'!

Junhyung and BTOB's Minhyuk, Sungjae, Changsub, and Hyunsik, who star as members of the idol group 'Men In Black' in the drama, and Ha Yeon Soo, who plays Min Sae Yi, have lent their voices for the song "Past Days". This is actually a fresh modern interpretation of Yoo Jae Ha's original song.

"Past Days" is the opening song for the premiere of 'Monstar', so you'll be hearing lot more of it through the show!