West of Shinjuku Station and close to Shinjuku Chuo Park, inside the unassuming Shinjuku NS Building, resides a 95-foot (29.1 meters) pendulum clock made by Seiko that was once listed as the world's largest.

The Yukku-Rhythm Grand Pendulum Clock is gigantic with a pendulum that is around 72 feet (22 meters) in diameter with a pendulum that takes 30 seconds to swing. Yukku-Rhythm is a fanciful portmanteau that derives from yukkuri "slow" and rizumu "rhythm," referring to the way its hand completes its full circle taking 24 hours.

Each of the hours on the clock face is represented by the Chinese zodiac, in keeping with the Asian tradition. Though obsolete, some of this tradition persist to this day, such as the phrase ushi-mitsu-doki "third hour of the ox" being the Japanese equivalent of the witching hour.

Outside of the atrium clock, the building has several restaurants and a viewing gallery that provides vistas of neighboring buildings. The building's name came from its co-developers, Nihon Seimei and Sumitomo, who are the building's primary occupants.