"....the flair and attack they showed in dispatching joint-favourites Nigeria impressed all who witnessed it."
-- Ludo Bagman reporting in the Daily Prophet, 2 July 2014 (Pm)
Ryuichi Yamaguchi was a Chaser for Japan’s National Team at the 2014 Quidditch World Cup.
Other canon notes and references
Ryuichi derives from 竜, 龍 (ryuu) meaning "dragon" and 一 (ichi) meaning "one". He may also be named after the award winning Japanese musician and composer Ryuichi Sakamoto.
Yamaguchi derives from Japanese 山 (yama) meaning "mountain" and 口 (kuchi) meaning "mouth, entrance" (Behind the Name).
From the Web
Screenshots of the Daily Prophet's coverage of the 2014 Quidditch World Cup: http://imgur.com/a/AXutv