After melting the hearts of fans with their unique webtoons marketing style, WM Entertainment's newest boyband, 'B1A4', has finally made their debut on today's episode of "M! Countdown"! Their unique name is an abbreviation of 'Be the one, All for one', and also stands for Baro being type B blood, while Jinyoung, CNU, Sandeul, and Gongchan being type A. Their title track, "OK", is an electronic track using rock as its base to feature the powerful and refreshing vocals of B1A4. With a catchy hook like, "Everything's OK as long as I have you", and an addictive melody to boot, the group seems to have what it takes work their way up to 'becoming the ultimate'. Check out their debut below!