The Shinhwa brothers showed their strong friendship on stage over the weekend.
Shin Hye Sung had a surprise guest in the form of Lee Min Woo at his Tokyo Dome City Hall concert on January 12.
The two got together on stage during Shin's cover performance of PSY's "Gangnam Style" and Shinhwa's "I Pray 4 U".
"I think you know who this is," the 33-year-old said of Lee to a 7,000-strong audience.
During the night, Shin performed hits like "Come Back" and "Same Thoughts" as well as covers of Taetiseo's "Twinkle" and Lee Hyori's "10 Minutes".
It had already been a successful few nights for the singer, who had earlier played at the Zepp Namba Osaka venue on January 9 and 10.
Shinhwa have announced that will celebrate their 15th anniversary in March with a tour and new album.