Tokyo stocks opened lower Friday as investors opted to secure profits following the Nikkei's 13-day winning streak and on concerns the market may be overheating.

As of 9:15 a.m., the 225-issue Nikkei Stock Average dropped 79.91 points, or 0.37 percent, from Thursday to 21,368.61.

The broader Topix index of all First Section issues on the Tokyo Stock Exchange, meanwhile, lost 5.60 points, or 0.32 percent, to 1,724.44.

Marine transportation, securities and bank-oriented issues comprised those that declined the most in the opening minutes after the morning bell.