Risa Niigaki
In September 2007, Okai was added to a new unit called Athena &amp; Robikerottsu with Risa Niigaki, Aika Mitsui, and Saki Nakajima. They sang the opening and ending theme songs for the A-1 Pictures anime "Robby &amp; Kerobby". The unit was effectively disbanded in March 2008, entering into an indefinite hiatus when the series ended.