Established in April 2015, the sub-unit consists of three members: Block B's two main dancers, B-Bomb and U-Kwon, and the rapper P.O.
[2] On April 5 and 6, 2015, Block B announced through solo teaser photos that P.O, U-Kwon, and B-Bomb would make up Bastarz.
In October 2015, Bastarz made their Japanese debut with the release of the CD single Hinko Zero, which reached #20 on the Oricon chart.
[9] A follow-up single, titled "Make It Rain," composed by Dean, was released on October 31 along with the full Welcome 2 Bastarz extended play,[10] which debuted at #6 on the Gaon album chart.
[11] The following week, the sub-unit made a surprise video release for the song "That's Right," featuring the members filming each other as they travel.