The band (with members Yonghoon, Harin, Kanghyun, Dongmyeong, and CyA) previously debuted in 2015 under Modern Music as MAS 0094. They later signed to RBW and promoted under the name MAS, and the members competed on shows including “Produce 101 Season 2” and “The Unit.” They are now re-debuting as ONEWE (pronounced '1-we') in May.
ONEWE’s brother group ONEUS debuted in January. ONEWE and ONEUS shared the single “Last Song” together in September. [Fun fact: they can be called literal brother groups as ONEWE member Dongmyeong and ONEUS member Xion (real name Dongju) are twin brothers.]
Source: ONEWE, Soompi