Young Japanese jazz trombonist from the short story "The King of Jazz" by Donald Barthelme. It first appeared in The New Yorker, January 30, 1977. At a gig with new "king of jazz" Hokie Mokie, he challenges Mokie's song choice ("Smoke"), and Mokie, and finds Mokie calling him the king of jazz after jamming together on "Billie's Bounce." But then Mokie comes back on Yamaguchi's best tune, "Cream," and takes back his title.
Yamaguchi heads back to his hometown of Tokyo to learn and study more.
Yamaguchi plays bent over, with his head between his knees. Which seems extremely difficult with a trombone.