The song "Proof" was the first ending theme to the anime Hayate the Combat Butler that aired with episodes one to thirteen.
The song "Get my way" was the second ending theme to the anime Hayate the Combat Butler aired from episode fourteen to twenty-six.
The song "Chasse" is the third ending theme to the anime Hayate the Combat Butler which began airing at episode twenty-seven.
Oto no nai Yozora ni/Ko no me kaze (音のない夜空に/木の芽風) is IKU's debut single released on March 19, 2008 in Japan by Geneon.
The song "Ko no me kaze" is the fourth ending theme to the anime Hayate the Combat Butler which began airing at episode forty.
The first two albums, released on May 25, 2007, include songs by Ryōko Shiraishi as Hayate Ayasaki and Rie Tanaka as Maria.
The next two, released on July 25, 2007, include songs by Rie Kugimiya as Nagi Sanzenin and Shizuka Itō as Hinagiku Katsura.
Volumes five and six, released on September 21, 2007, contained songs by Miyu Matsuki as Isumi Saginomiya and Kana Ueda as Sakuya Aizawa.
Album number nine, released on January 25, 2008, includes songs by Hitomi Nabatame as Yukiji Katsura, and volume ten released on the same day is a trio between Eri Nakao, Sayuri Yahagi, and Masumi Asano as Miki Hanabishi, Izumi Segawa, and Risa Asakaze respectively.