Ko Otani - Wondering
Ko Otani - LOVE WILL LIGHT THE WAY
Otani Ko - Tegami ~Haikei Juugo no Kimi he~
Otani Ko - Tegami ~Haikei Juugo no Kimi he~ (Многоцветье)
Otani Ko - Free Bird (Haibane Renmei OST)
Otani Ko (Haibane Renmei) - Blue Flow
Otani Ko - Wondering (Haibane Renmei OST)
Otani Ko - 手紙 ~拝啓、十五の僕には~