I feel this non-korean group fits the closest to the definition of a Kpop group.

[GuardianofTheCosmicRealm]

Disbanded vietnamese group LIME. Compared to Zgirls\Zboys, UHSN, EXP Edition and lately Lalary, LIME trained for two years in Korea, took korean lesson and sang in korean. Many koreans said their pronouncement were good and they were often mistaken to be korean as well.