Monaca (2005–present)
Kōsaki's first major project with Monaca was the soundtrack for the 2006 anime television series The Melancholy of Haruhi Suzumiya. Series production director Yamamoto recommended Kōsaki as the composer for the anime, who found it difficult to get involved in such a large scale project outside of Namco, serving as another reason for quitting the company to join Monaca.[9] An album containing three of his compositions ("God knows...", "Lost my music", and "Koi no Mikuru Densetsu") for the anime sold more than 136,000 copies in Japan and peaked at #5 on the weekly Oricon Singles Chart.[10] "God knows..." in particular has received a lot of acclaim, although Kōsaki found it challenging to compose due to having little experience with band recording and playing guitar,[9] so he studied band rock music. Although he often incorporated live musicians in his previous Namco work, this served as the first time he composed a track fully performed by a band.[3]
In 2007, he composed the soundtrack for the anime television series Lucky Star; the series' opening theme "Motteke! Sailor Fuku" peaked at #2 on the chart upon release.[11] It would also go on to win the 2007 Radio Kansai Award, a subset of the Animation Kobe Theme Song Award.[12] He found the workload overwhelming, as prior to joining Monaca he was not used to composing a large number of tracks under time constraints.[9]
He served as the lead composer for Bakemonogatari in 2009, composing all of the background music and most of the songs. The song "Renai Circulation", features lyrics by Meg Rock and vocals by Kana Hanazawa as character Nadeko Sengoku. Kōsaki felt it would be interesting to feature Hanazawa rapping, inspired by Shibuya-kei group Kaseki Cider. The song received acclaim in particular and inspired a wave of cover dances and mash-ups on Niconico during the 2010s. It later found further popularity on TikTok in the late 2010s, which intrigued Kōsaki as many people who listened to it did not know about it at the time of release.[13]
In December 2010, he announced an indefinite hiatus from his work due to poor health.[14] He began a second illness-related hiatus in February 2014[15] and returned to work in January 2015.[16] During this time, he re-studied music theory, as he previously felt insecure about not having formal music education.[13]
In 2019, he worked on the anime Beastars, which features gypsy-inspired music.[17] In 2020, a compilation album titled Satoru Kosaki 20th Anniversary Selected Works "DAWN" was released to commemorate 20 years of being a composer. It includes a selection of his most successful songs, while the limited edition release also includes a selection of anime BGM.[18][19] In 2021, he composed for the anime Vivy: Fluorite Eye's Song; the following year, the anime won the Best Music Anime award at AniTrendz's 8th Annual Anime Trending Awards.[20]
