Collaboration: Gre4n Boyz 5k263

Greeeen (stylised as GReeeeN) is a Japanese pop/rock/hip hop/breakbeat vocal group from Koriyama city in Fukushima Prefecture, comprising the all-male four Hide, Navi, 92, and Soh. They made their debut under the label Nayutawave Records of the Universal Music Japan in January 2007 with the single Michi. Their logo image is of a mouthful of teeth, and the four Es indicate the number of . The sound production is handled by Hide's older brother JIN, a former guitarist of Pay money To my Pain. According to their website at Universal Music Japan, their catch phrase is "Rock 'n' Breakbeats with Four Microphones".

One notable characteristic is that none of the have ever shown their faces in the public sphere as a part of GReeeeN, whether in their promotional videos, CDs, television performances, or the Internet. In their only performance on TV-U Fukushima's music show Music Bar Palo Palo (broadcast on January 19, 2007), the group even went as far as censoring their faces during the performance. GReeeeN cites keeping their professional lives in dentistry compatible with their musical ventures as the reason, but one of the , Hide, has hinted that after all of the the prefectural examination in dentistry and receive permission from the directors of the hospitals they work for, the group may consider a public appearance.

All studied at the dentistry department at Ohu University in Fukushima Prefecture and the group debuted while still in school in 2007.

The of the popular band GReeeeN have finally achieved their goal, because all have ed their dentistry exams.

The ' identities are still unknown, as their faces have never been made public. At first, the group stated that they would wait until all of the ed the exam before revealing their faces, but in 2009 they indicated that they will still keep their identities secret to avoid any interference with their careers as dentists.

On March 19, 2024 they announced that they changed the name of the group from GReeeeN to Gre4n Boyz.