Exiting the Nanboku subway's Korakuen Station near Tokyo Dome, I gaze up at clouds resembling bunches of purple hydrangeas. Directly overhead, a roller coaster car swooshes by, its passengers shrieking, which is a good sign, because, despite its aquatic name, the Thunder Dolphin coaster doesn't run in rainy weather. Optimistic, I head west along Metropolitan Road 434, into the Koishikawa neighborhood.

Striding by a building with six small storefronts — neighborhood tobacco stall, bar, gyoza joint, shuttered place — the fifth place stops me in my tracks. The Tokyo Accordion Culture Club? Catching sight of me, Xi-an Yu waves me in. The soft-spoken 61-year-old, hailing from Shanghai, teaches his more than 50 students how to orchestrate the bellows, keyboard, bass buttons and couplers of the complex instrument.

"My oldest brother, who was rather scary, forced me to learn the accordion at age 4," Yu recalls. Despite losing what many musicians would consider his prime learning years to the deprivations of China's Cultural Revolution (1966-76), Yu nonetheless won a contest at the Shanghai Opera House in 1972, and the accordion became his lifelong squeeze. Before I leave, Yu slides his accordion over his shoulders, and fills the classroom with a melancholic riff so beautifully phrased that it moves me.