Cognomen Usui (ウスイ 
, Usui 
, Усуи 
) , in the world, is quite a rare family name. The family name Usui is habitual in Hong Kong, where it is a rare surname, Japan, and Sri Lanka. Not in comparison with a country's population, it most frequently occurs in Japan, the United States, and Indonesia. More frequently, Usui is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| ウスイ | Japan |
| Usui | Brazil, Japan, Indonesia, United States, China |
| Усуи | Russia |
| bumpei usui Japanese-born artist and art collector, JP (b. 1898) |
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mikoto usui Japanese sustainability advocate, JP |
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takanobu usui Japanese skeleton racer, JP |
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| kazuo usui (b. 1953) |
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| rena usui researcher |
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| k. usui botanist |
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| kazuteru usui researcher |
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| tatsufumi usui researcher (ORCID 0000-0003-1726-1293) |
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| yuriko usui researcher (ORCID 0000-0002-6224-5391) |
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| masaru usui researcher |
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| fumihiko usui researcher |
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| kenji usui researcher ORCID ID = 0000-0003-4558-5762 |
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| usui hiroyuki Japan esperantist |
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| yoshiaki usui researcher |
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| akihito usui researcher |
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