Ota won the bronze medal at the 2000–2001 Japan Junior Championships. In the 2001–2002 season, Ota made her Junior Grand Prix debut. She won her event in Bulgaria and placed 4th at the event in Sweden to qualify for the Junior Grand Prix Final, where she placed 6th. She won a second bronze medal at the 2001–2002 Japan Junior Championships, which qualified her for the 2002 Junior Worlds. She placed 9th at that competition. In the 2002–2003 season, Ota competed on the 2002–2003 ISU Junior Grand Prix circuit. She won both her events to qualify for the Junior Grand Prix Final, which she won. She placed fourth at the Japan Championships and qualified for Junior Worlds. She won the 2003 World Junior title. In the 2003–2004 season, Ota made her senior international debut. She competed on the Grand Prix of Figure Skating. She placed 4th at the 2003 Skate Canada International and 6th at the 2003 NHK Trophy. At the Japan Championships, Ota placed fifth. She competed at the 2004 Four Continents and won the event after placing third in the short program and second in the free skate. In the 2004–2005 season, Ota competed again on the senior international circuit. She placed 7th at the 2004 Skate America.