"Kōsui" (香水, lit. "Perfume") is a song by Japanese singer and songwriter Eito from his debut studio album, Sukkarakan (2021). The song was initially self-released for digital download and streaming on 21 April 2019 as the singer's debut single, and later released through A.S.A.B. "Kōsui" is an acoustic guitar-laid J-pop song, inspired by his experience of breakup.
The song gained national recognition after it became a viral hit on TikTok with users covering the song. Its popularity on the social media app is credited to the lyrics with the incorporation of the memorable proper nouns such as Line and Dolce & Gabbana.
In Japan, "Kōsui" became Eito's breakthrough hit, topping the BillboardJapan Hot 100 and the Oricon Weekly Singles Chart, as well as topping on the Spotify Global Viral Top 50. As of August 2020, the song has been streamed over 100 million times. The cover videos of the song filmed by celebrities boosted its popularity and made Eito the household name. The celebrities such as Shingo Katori, Chocolate Planet, Misako Uno, and Naoto Inti Raymi have covered the song so far. On 31 December 2020, Eito performed the song at the 71st Kōhaku Uta Gassen, one of the most prestigious music festival in Japan.
On 4 May 2020, "Kōsui" debuted on the BillboardJapan Hot 100 at number 34, boosted by the popularity on TikTok. On 25 May 2020, it peaked on the chart at number one. As of 25 November 2020, the song has stayed on the chart for 30 consecutive weeks.
The music video for "Kōsui" was directed and filmed by Keita Inaba. The video was released on YouTube on 28 May 2019, and has accumulated over 124 million views as of November 2020. The video features Eito singing over the acoustic guitar, played by Junnosuke Onodera, and the contemporary dance played by Akari Kamayachi.
