Big Brain is a South Korean R&B ballad group, formed under the label World Show Market. The group, consisting of vocal performance students Mo Sang Hoon, Kim Jin Yong, Hwang Byeong Eun, and Yoon Hong Hyun, officially debuted in 2015. Since the beginning of their career, the four-piece drew comparisons to notable groups like Brown Eyed Soul and Big Mama. Originally known as The Man, they changed their name to avoid confusion with a senior group. Before their official debut, Big Brain had already made a mark by busking in New York City, performing at iconic locations like Times Square and Central Park. Their debut album Billionaire Sound came out in 2015 and featured the single "Welcome," an emotional ballad blending R&B with a contemporary approach. In 2016, Big Brain continued to gain momentum, notably opening for Olivia Newton-John. They also released several mini-albums throughout the year, including Brain's 1st Respect (2015), The Voicist (2016), meet you.. (2016), and The Moment (2016), with each release showcasing their soulful R&B style.