He won the 10,000 metres gold medal at the 2011 Summer Universiade in Shenzhen and holds the Asian junior record for the half marathon.

He was the fastest in his stage at the Japanese High School Ekiden Championship and came second in the junior race at the Chiba Cross Country.

On the track that year he set a personal best of 28:35.75 minutes in Tokyo then finished eighth at the 2010 World Junior Championships in Athletics.

In November he ran at the Ageo City Half Marathon and set a Japanese and Asian junior record time of 1:01:47 hours to win the race.

[3] Osako was chosen to represent his country at the 2011 Summer Universiade, where he defeated Stephen Mokoka in the 10,000 m to take the gold medal, becoming the first Japanese since Yasuyuki Watanabe [jp] to win that title.