The unbeaten 21-year-old, nicknamed “Monster”, was in control from the start of the bout, putting his 39-year-old opponent to the floor three times, before finishing the contest with a powerful left body punch that kept Narvaez, who had defended the WBO belt for 12 years,??on his knees.
“I have practiced the body punch, and I thought I can bring him down if I could find opportunities to use it,” Inoue said.
“I appreciate this opportunity to fight the super champion (Narvaez) in Japan.”
Inoue, who had moved up two weights for the fight after claiming the WBC light-flyweight crown in April, now has a record of seven knockouts in his eight unbeaten fights as a professional.
The bout was part of a triple header that also saw Mexican Pedro Guevara secure the WBC light-flyweight title by flooring Japanese fighter Akira Yaegashi.
Guevara’s seventh-round knockdown with a stunning body punch denied Yaegashi’s attempt to win his third world title.
Meanwhile, Jorge Linares of Venezuela won the WBC lightweight title by beating Mexico’s Javier Prieto.
Linares collected his third world title with a fourth-round knockout, after winning the WBC featherweight and the WBA super featherweight titles.