Kobayashi moved up to specialise in longer distances and ran the 5000 m at the 2008 Beijing Olympics after becoming the Japanese national champion in the event.

She gave the best performance by an Asian runner in the women's 5000 m at the 2009 World Championships in Athletics, finishing in eleventh and beating her domestic rival Yurika Nakamura.

[2] She was selected to represent Asia/Pacific at the 2010 IAAF Continental Cup, but managed only eighth place in the 3000 m. The following January, she ran for Hyōgo at the 2011 Women's Inter-Prefectural Ekiden and set a new stage record in her section, although the team finished in ninth position overall.

[3] She was the bronze medalist in the 5000 m at the 2011 Asian Athletics Championships in Kobe, one place behind her compatriot Hitomi Niiya.

[4] At the International Chiba Ekiden in November she won the first women's stage for Japan, setting a race record for her leg, and the mixed team went on to finish a close second behind Kenya.