Oshima represented
Japan at the 2002 Asian Games and won a bronze medal in the team competition. She competed on the vault and the floor exercise at the 2002 World Championships but did not advance into either event final. At the
2003 Asian Championships, she won a silver medal in the team event and also won a bronze medal on the balance beam, behind
Zhang Nan and
Fan Ye. She then competed at the
2003 World Championships, where Japan placed 14th in the team qualifications. Oshima was selected to represent
Japan at the 2004 Summer Olympics. She finished 51st in the all-around
qualifications and did not advance into any finals. At the
2005 East Asian Games, she won the all-around bronze medal and a team silver medal. She advanced into the all-around final at the
2005 World Championships and placed 19th. She helped Japan win the team bronze medal at the
2006 Asian Championships. She also helped Japan win the bronze medal at the
2006 Asian Games, which was later upgraded to a silver medal after North Korea was disqualified for age falsification. Oshima finished 34th in the all-around qualifications at the
2006 World Championships, making her the fourth reserve for the final. She competed with the Japanese team that placed 12th at the
2007 World Championships. Oshima won the all-around title at the 2008 NHK Cup, her first time winning the competition since 2002. As a result, she was selected to represent
Japan at the 2008 Summer Olympics alongside
Mayu Kuroda,
Yu Minobe,
Yuko Shintake,
Kōko Tsurumi, and
Miki Uemura. She helped Japan advance into the team finals in eighth place, and she also advanced into the individual all-around final. Oshima competed on three events during the team final to help Japan finish fifth. She then finished 20th in the
all-around final. After the Olympic Games, she helped the Japanese team win the gold medal at the
2008 Asian Championships. Oshima competed on the uneven bars and the floor exercise at the
2009 World Championships but did not advance into either apparatus final. She represented
Japan at the 2010 Asian Games, helping the team win the silver medal behind China. At the
2010 World Championships, she finished fifth with Japan in the team final. Oshima won a silver medal with the Japanese team at the
2011 Summer Universiade. She then competed at the
2011 World Championships, where Japan finished seventh in the team final. She was not selected to compete at the
2012 Summer Olympics. ==References==