The event will take place at the Nakano Sun Plaza Main Hall at January 22. There will be two performances on one day, with the first set starting at 3PM and the second one at 6:30PM.
While N:SONIC just debuted just had its debut a few months back, SMASH has been working on their Japanese career since the release of "Lunatic" at the end of 2010. Their 5th Japanese single "Step" was released at the Beginning of November.
SMASH is said to be in preparation for a Korean comeback though more information on the matter hasn't been officially revealed.
Source: SMASH