Mr. Echigoya grew up in coastal Wakkanai, on the northern tip of Japan. In 1996, he moved to the Bowery area in New York to start a fashion line. He ultimately took that line to Japan where, in 2013, he learned, by plying Chinese factory workers with sweets, how to sew denim. In 2014, he returned to New York and two years later, he started Bowery Blue Makers.

His native country still plays a part in the jeans-making process: Mr. Echigoya sends American cotton to Japan to be dyed; then it is returned to him to sew.

Usually, Mr. Echigoya produces about 25 pairs a month, which sell for $480 and $580 each from his website, boweryblue.com, and for as much as $650 at shops in Brooklyn, Tokyo, Hong Kong and Bangkok.

“You said straight leg, right?” Mr. Echigoya asked Mr. Mosholder, handing him two pairs and leading him to a makeshift dressing room in a hallway. He pulled shut a gray curtain.