Itsuka no, Ikutsuka no Kimi to no Sekai (いつかの、いくつかのきみとのせかい)

"Itsuka no, Ikutsuka no Kimi to no Sekai (いつかの、いくつかのきみとのせかい)" is a song by fhána that served as the first opening theme for the 2014 television anime Bokura wa Minna Kawai-sou (僕らはみんな河合荘), which was animated by Brain's Base. fhána released it on May 28, 2014 as the group's fourth single.

林英樹 wrote the lyrics, 佐藤純一 composed the music, and fhána arranged the title track. The single also included the B-sides "ケセラセラ" and "はじまりのサヨナラ" as well as instrumental versions, and the song later appeared on fhána's first album Outside of Melancholy, released on February 4, 2015.