That night, Blue in Green was hosting a pop-up for the Japanese brand Creek Angler’s Device, a sort of if-you-know-you-know (and my husband knew) name in stylish fly-fishing-inspired gear.

Considering Alex Mill is a clothing brand that champions subtlety and curation, Alex Drexler’s office is what you might expect of the 37-year-old founder. Shirts made of Japanese fabric and t-shirts ...