Gradation Heart: Koi no Kenkyuu Okotarazu
Gradation heart～恋の研究おこたらずっ～
Year: 2012
singer Tomatsu Haruka
singer Nazuka Kaori
singer Toyosaki Aki
singer Kugimiya Rie
singer Tange Sakura
singer Inoue Kikuko
singer Shintani Ryouko
singer ラブ♥ステ
lyrics Mieno Hitomi
composer Okamoto Kensuke
