Many of her songs in Slayers, (such as Get along, KUJIKENAIKARA!, and Nemurenai Yoru Wa) are performed in duet with Megumi Hayashibara. Moreover, most of Okui's work with Slayers is related to the first and second seasons of the anime, and with the earlier radio dramas, Slayers EX and Slayers N►EX. She has performed no songs in the later Slayers works, including Slayers TRY, Slayers REVOLUTION, or Slayers EVOLUTION-R, with the exception of playing the chorus in Plenty of grit. Why this is the case is unclear.