"Nagging" (Korean: 잔소리; RR: Jansori)[1] is a song recorded by South Korean singers IU and Lim Seulong.

Written by Kim Eana and composed by Lee Min-soo, the pop ballad duet was used as one of the theme songs for the second season of the variety show, We Got Married, along with "We Fell in Love" by Jo Kwon and Ga-in.

[2] The song was released in South Korea on June 3, 2010, and was re-released under the title "Ko Go To" (コ・ゴ・ト) on December 14, 2011, as part of IU's first Japanese extended play I□U (2011).

The song was a commercial success in South Korea.

The single debuted at twelve on the Gaon Digital Chart and shot up to number-one position the following week, where it remained for three weeks.