The popular district of Kichijoji, in western Tokyo, is the place to hunt for vintage clothes and quirky antiques, enjoy drinks and food in the narrow alleyways called Harmonica Yokocho, or ride the swan boats in scenic Inokashira Park.

Right at home in this buzzy area is a shop called Masa’s Pastime, specializing in antique pocket watches and repairs. But its founder and president, Masa Nakajima, has turned the business into more than a pastime over the years.

And this spring he plans to introduce two iterations of an original watch — not yet named — that he created with his team of watchmakers, most of whom are recent graduates of the Hiko Mizuno College of Jewelry.

Masa’s Pastime does a lot of things. “We sell antique watches, mostly pocket watches that are around 300 years old, and custom-made watches we made using the antique movements from pocket watches and creating a new case, dial and hands,” Mr. Nakajima said, displaying a wristwatch with a black carbon-coated steel case (1.1 million yen, or $7,455). It was powered with a 100-year-old Hamilton pocket watch movement, he said, noting, “those old pocket watch movements were not only of good quality and beautifully finished, but also durable.”

His workers also do repairs (walk-ins are welcome), special commissions (for example, customers can have the movement of an antique pocket watch put into an original case created in the shop), and customizations such as engraving or blued screws, a decorative element in movements.