|Birth name||Kōsei Ono|
|Date of birth||April 17, 1987|
|Place of birth||Nagoya, Aichi Prefecture, Japan|
|Height||1.71 m (5 ft 7 in)|
|Weight||83 kg (13 st 1 lb; 183 lb)|
|School||Christchurch Boys' High School|
|Rugby union career|
Ono moved to New Zealand aged 3, and went to Christchurch Boys' High School, the school that famously has produced 46 All Blacks in total including the likes of Andrew Mehrtens and Dan Carter. Ono played alongside future All Blacks Owen Franks and Colin Slade as part of the 2004 squad that went unbeaten.
He moved back to Japan to play for the Fukuoka Sanix Blues and made his debut against Korea just 5 days after his 20th birthday as the joint 12th youngest player of all time to represent Japan in April 2007. He won four more caps that year including one at the 2007 Rugby World Cup against Australia. But then after the tournament Ono was not selected by coach John Kirwan who preferred James Arlidge and Shaun Webb at fly half.
In 2012 Ono was named in the Top League team of the season and was brought back into the team by new coach Eddie Jones after four-and-a-half years since his last cap and established himself as first choice fly half and as yet has only missed one international game since Jones took charge. Notably in November 2012, Ono made important contributions on Japan's successful tour of Eastern Europe with a great tactical kicking performance in Romania and then the following week he scored a last minute winning drop goal against Georgia.
For the 2012–13 Top League season he moved from the Fukuoka Sanix Blues to the reigning champions Suntory Sungoliath forming a half back combination alongside former Springbok Fourie du Preez and helped them to retain their title and go the season unbeaten. Ono was again named in the Top League team of the season for the second year in a row.
- "Ono: Larkham doesn't have a weakness".
- "Schools supplying most All Blacks, Dan Carter's goal-kicking and Elton Jantjies".
- "Breakthrough! 2004 Christchurch Boys' High School 1st XV".
- "Japan / Youngest appearance". Archived from the original on 2013-11-09.
- "Le XV type de Top League 2011/2012".
- "Kosei Ono astute tactical kicking vs Romania".
- "Last minute winning drop goal by Kosei Ono vs Georgia 2012".
- "Le XV type de Top League 2012/2013".