semi-organized crime group; non-yakuza gang
Refers to criminal groups that are not part of traditional yakuza organizations, often consisting of younger members and operating in a more fluid, less hierarchical manner. The term is a blend of 半 (half) and グレる (to go astray/delinquent).
See also: ぐれる
Recently, crimes by semi-organized gangs have been increasing.
He is known as a leader of a non-yakuza crime group.