The first thing you notice about architect Yuko Nagayama is her youth. She looks far too young to have built a five-story commercial building in Tokyo's upscale Minamiaoyama area, a stunning boutique for Louis Vuitton in the heart of Kyoto, and shops for the handbag brand Anteprima all over Asia. No wonder. The 37-year-old architect launched her practice when she was only 26.

At that time, she had just left the office of Jun Aoki, a principal who encourages employees to exit after four years to infuse his firm with a steady supply of fresh blood. During her tenure, Nagayama acquired essential practical experience by working on houses and the Aomori Museum of Art. To assist his young prot'g'e as she went out on her own, Aoki sent her off with a commission for a salon in Tokyo's trendy Omotesando district.

That first project, the two-story salon called Afloat-f, was completed in 2002. It features 22 eight-foot-wide satellite dishes doubling as suspended reflectors, illuminated by uplights centered below each one, above the hairstyling area. With that stunning debut the architect won a string of commissions. Three years later Nagayama finally had time to catch her breath and take her licensing exam.

Today she runs her four-person firm from two apartments in adjacent residential buildings on the western edge of Tokyo. One gives her space to bring her baby without disturbing her staff; the other centers on a small meeting room where a vintage wooden drawing desk serves as the conference table.

Balancing motherhood and work, Nagayama is engaged in an impressive lineup of projects that includes residences, cake shops, and a museum on Teshima, an island in the Seto Inland Sea put on the architecture map by Ryue Nishizawa's Teshima Art Museum. For a few young architects, designing on the island is an honor granted by Mitsuko Fukutake and the Fukutake Foundation, the group that turned nearby Naoshima into an art mecca. While Nishizawa's shallow concrete dome focuses on birth, Nagayama's museum addresses death.

To house the museum, devoted to works by the graphic artist Tadanori Yokoo, Nagayama is resurrecting a trio of 100-year-old residential structures. As part of her scheme, she is incorporating Yokoo's landscape installation symbolizing the afterlife and including a mini'River Styx that will run under the building. After the project's 2013 completion, a tatami-floored room inside will be available for funerals that were traditionally held at home. “Combining museums with other functions is a recent trend for the Fukutake Foundation,” she explains.

Though the museum/funeral hall may be a first, it isn't Nagayama's only unusual undertaking. She designed a surreal lounge for the Hotaruna, a cruise ship created by the anime artist Leiji Matsumoto. A floating bar by night and a rental space by day, the glass-roofed boat is one of Matsumoto's fantastic travel vessels come to life. Evoking its retro-futuristic image, Nagayama outfitted the interior with changeable stripes of colored lights embedded in the floor, chairs and tables that move up and down, and a bar clad with shimmering stainless-steel mesh.

As a mother, Nagayama finds it isn't easy to do it all. “[In Japan] it is rare for women architects running firms to have children,” she says. Most who do practice with their husbands. Many of Japan's most successful women heading practices—such as Itsuko Hasegawa, Kazuyo Sejima, and Kumiko Inui—don't have children. But thanks to her accommodating staff and an iPad, Nagayama sets an excellent example for her colleagues everywhere.