There's technically a sign outside, but it's tough to find. Instead, look for the red "on air" sign to point you in the right direction of Sake Bar Decibel. Once you see the sign, head down the stairs and see if there's a table open.
A wait is almost guaranteed for a seat at this small Japanese bar with a super sake selection, but it's absolutely worth your time. You'll be ushered into dark surrounds where you'll sit practically shoulder-to-shoulder with fellow sake sippers for an underground yet deliciously over-the-top escape.