Yuki Yamaguchi (山口 有希, Yamaguchi Yūki; born 22 February 1984 in Maizuru, Kyoto) is a former Japanese sprinter who specialised in the 400 metres. His personal best time was 45.18 seconds, achieved in the 2003 National Sports Festival of Japan in Fukuroi. This is the current Japanese junior record.
Source: “Yuki Yamaguchi”, English Wikipedia (CC BY-SA 4.0), excerpt