Ryo of Supercell was the one who composed the song's lyrics and arrangement of the track.  Originally, vocaloid Hatsune Miku was chosen as the vocalist for the closing theme as part of Supercell's self-titled debut album in March 2009.  Instead, Nagi Yanagi took over her place making their first release to not use a singing synthesizer.
Yanagi was chosen as the vocalist due to Ryo being a fan of her voice before uploading his songs to Nico Nico Douga in late 2007. Ryo's first song, "Melt", was covered by Yanagi roughly one day after the song's release on the platform. She herself was also a fan of Ryo's music and contacted him in collaborating songs together in the future.
|Original Japanese||Japanese Rōmaji||English Translation|
| itsumo-dōri no aru hi no koto|
kimi wa totsuzen tachiagari itta
| On a day just like any other,|
you suddenly stood up and said,
| "tama ni wa ii koto yuun da ne"|
nante minna shite itte waratta
| "I guess even you get a good idea sometimes,"|
everyone said as they laughed.
| makkura na sekai kara miageta|
yozora wa hoshi ga furu yō de
| As we gazed up from this pitch-black world,|
the stars looked like they were falling from the night sky.
| いつからだろう 君の事を|
| itsu kara darō, kimi no koto o|
oikakeru watashi ga ita
| Since when, I wonder,|
have I been chasing after you?
| "are ga DENEBU ARUTAIRU BEGA"|
kimi wa yubisasu Natsu no Daisankaku
| "That's Deneb, Altair, and Vega,"|
you say as you point at the Summer Triangle.
| tanoshige na hitotsu tonari no kimi|
watashi wa nani mo ienakute
| You are by my side, enjoying yourself,|
and I, am unable to say anything.
| hontō wa zutto kimi no koto o|
dokoka de wakatte ita
| The truth is, I've always|
known somewhere inside, my feelings for you.
| tsuyogaru watashi wa okubyō de|
kyōmi ga nai yōna furi o shiteta
| I pretend to be strong but am cowardly|
I pretended not to care.
| どうしたい？ 言ってごらん|
| dō shitai? itte goran|
kokoro no koe ga suru
| "What would you like to do? Tell me."|
I hear the voice of my heart.
| I didn't say it,|
I couldn't say it,
| ano natsu no hi|
| That summer day|
those twinkling stars
- ClariS, another artist who contributed closing theme songs of the series, covered their own version of Kimi no Shiranai Monogatari in their SHIORI single release in 2017.
- ↑ Kimi no Shiranai Monogatari / supercell. VGMdb.
- ↑ Album Using Voice Synthesizer "Hatsune Miku" Ranks 2nd on First Day. (in Japanese). Oricon. March 5, 2009. Retrieved October 6, 2017.
- ↑ Supercell Interview. (in Japanese). Hotexpress. August 12, 2009. Retrieved October 6, 2017.