Koiwai (written: 小岩井 lit "small rock well") is a Japanese surname. Notable people with the surname include:

• Eichi Karl Koiwai (1920–2009), American judoka
• Kotori Koiwai (小岩井 ことり, born 1990), Japanese voice actress
• Kumiko Koiwai (小岩井 久美子, born 1975), Japanese figure skater
• Sakura Koiwai (小祝さくら, born 1998), Japanese golfer

• Yotsuba Koiwai (小岩井 四葉), titular character of the manga series Yotsuba&!

• Yoshino Koiwai, character from Masamune-kun's No Revenge series

• Koiwai Station, a railway station in Takizawa, Iwate Prefecture, Japan

Surname list

This page lists people with the surname Koiwai.
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