SEE ALSO: 2AM members promise special treats for lucky selected fans if snow falls on the day of their concert

K.Will will make a special guest appearance at the '2013 2AM CONCERT-NOCTURNE' on the 8th and will perform two songs. 2AM previously performed at K.Will's solo concert last year and now K.Will will return the favor at their concert.

About their upcoming event, 2AM shared, "Compared to our concert last year, the concert repertoire changed a lot... There are a lot of songs that we need to practice for. Although there is pressure, we are working hard to create the best concert."

The ballad idols will hold their Seoul concert at SK Olympic Handball Gymnasium on December 7-8, and cross over to the States to perform in LA on the 15th, as well as Taipei, Taiwan on the 21st.