Starship Entertainment sprung a surprise late last month with the unveiling of SISTAR's sub-unit, SISTAR19 comprising of members, Hyorin and Bora and they made their debut on today's KBS's Music Bank with their debut single, "Ma Boy"! In contrast to the high tension music video teaser, the song is sweeter in quality. The girls have been working with Brave Brothers since their debut, and he's their producer once again for this romantic track about the nervous feelings of a young woman in love. As expected, Hyorin's explosive vocals and Bora's rapping are a perfect match! So check out their debut stage below!