On 30 July 2012, Karunaratne defeated world eighth-ranked Kenichi Tago of Japan 2–0.
Karunaratne defeated Tago 21–18, 21–16 in 44 minutes at the Wembley Arena in the Olympic men's badminton singles Group C at the 2012 Summer Olympics.
 The Associated Press quoted him as saying: "This is the biggest win in the history of Sri Lanka badminton".
India's Parupalli Kashyap sent him out of the Games, in a closely fought pre-quarter match.
On 30 July 2012, Karunaratne defeated world eighth-ranked Kenichi Tago of Japan 2–0. Karunaratne defeated Tago 21–18, 21–16 in 44 minutes at the Wembley Arena in the Olympic men's badminton singles Group C at the 2012 Summer Olympics.  The Associated Press quoted him as saying: "This is the biggest win in the history of Sri Lanka badminton". India's Parupalli Kashyap sent him out of the Games, in a closely fought pre-quarter match.
Niluka Karunaratne