Undercover is anything but. The 20-m-long unanchored tube in the backstreets of Harajuku—Ura-Hara in trendyspeak— is the press showroom of street-fashion pioneer Jun Takahashi's Undercover clothing line. Adjoining this is a 10-m -high, '60s-style living room that completes one of Tokyo's most striking office spaces.

"We are not afraid of taking a new approach to a project," explains architect Astrid Klein on behalf of Klein Dytham Architecture (KDa), the creator of Undercover's funky Harajuku home. Klein and her partner, fellow architect Mark Dytham, founded Tokyo-based KDa in 1991. Their Idée Work Station, a furniture showroom that in 1996 netted two prestigious design awards, established KDa as a cutting-edge studio in architecture, interior and furniture design. (Check out KDa's oeuvre at klein-dytham.com.)

Interior designer Masamichi Katayama has also given Ura-Hara its signature nonsartorial style, conceiving interiors for fashion line A Bathing Ape (Bape). Since collaborating with Bape's creator Nigo on the company's Busy Work Shop in 1998, Katayama has produced 15 Bape shops in Tokyo, Osaka and London. The most innovative was the Baby Milo Store—a mix of 2001: a Space Odyssey and Planet of the Apes centered on a carousel of ape dolls riding on robotic horses.

Katayama, who has also designed Marc Jacobs' Aoyama boutique and The Bank, a minimalist, Zen-style take on the traditional shot bar, says, "My taste keeps changing, and I don't think it is right to suppress the desire to change. Call me a workaholic, but to me this is not work, it's fun." (See more of his designs at www.wonder-wall.com.)