Kosei is a very rare boys' name that peaked in 2008 and has since faded.
Kosei is a boy name. It last appears in U.S. records in 2020. Kosei first appears in 2000 and peaked in 2008 (9 births).
| Year | U.S. births | U.S. + territories | Rank |
|---|---|---|---|
| 2020 | 7 | 7 | #10,149 |
| 2019 | 5 | 5 | #13,244 |
| 2018 | 6 | 6 | #11,557 |
| 2016 | 5 | 5 | #13,349 |
| 2014 | 5 | 5 | #13,186 |
| 2013 | 6 | 6 | #11,546 |
| 2012 | 5 | 5 | #13,351 |
| 2011 | 5 | 5 | #13,463 |
| 2010 | 6 | 6 | #11,578 |
| 2009 | 6 | 6 | #11,824 |
| 2008 | 9 | 9 | #8,703 |
| 2006 | 5 | 5 | #13,161 |
| 2004 | 5 | 5 | #12,405 |
| 2003 | 5 | 5 | #11,949 |
| 2002 | 5 | 5 | #11,709 |
| 2000 | 5 | 5 | #11,407 |