Earlier in her career, Arai was a frequent runner-up to Minori Hayakari at the Japan Championships in Athletics, but she took national titles in both 2012 and 2013.

She was chosen for the 2007 Asian Cross Country Championships in March and came eighth, helping the Japanese women's team (including Minori Hayakari and Eri Kotake) to second in the rankings.

[2] She gradually improved her steeplechase best in the outdoor track season, coming third at the Oda Memorial and culminating in a personal best of 9:57.02 minutes for second at the National Championships.

[4] Arai focused on the steeplechase in 2008 and dipped under ten minutes again at the Barcelona Meeting, but was some way behind Hayakari and Kazuka Wakatsuki and the Japanese Championships and was not selected for the 2008 Beijing Olympics.

[10] Arai returned to competition in 2012 and won her first national title at the 2012 Japan Championships in Athletics, as compatriot Hayakari (nearing forty) faltered in the final.