According to ELIAS

Twins are first team to beat the Royals in 2015

The Twins defeated the Royals on last night and handed Kansas City (now 7-1) its first loss of the season. Since the franchise moved to Minnesota for the 1961 season, the Twins had never before defeated an opponent that was undefeated at least five games into its season. They recorded wins over that span against three teams that were 4-0: the 1992 Rangers, 1996 Orioles and 2004 Tigers.