This song was released in the 3-disc Yours album by dai from Comiket 72. I’m not sure if the song was used in the PC game.
The significance of this song is that it is the first in a series of four songs from the Yours album that seem to describe Sonozaki Shion and Hojo Satoshi’s relationship and Satoshi’s recovery from a coma while Shion patiently watches over him for two years. Listen to the songs in order (Sorayume, Sora no Mukou, Confession, Thanks). They’re very emotional.
Even if the songs aren’t all that stellar, it’s all worth it for the last line of the fourth song, Thanks.
When I suddenly realized it, it’s nighttime
Illuminated by the moonlight, I am pulled back by the reality
As if the fog lifted
What was I doing?
My heart is tightly bound by my reviving memories
Nothing could be done and I’m suffering
Why didn’t I worry?
Everything was completely a nightmare
Inside of the deep darkness
If I can redo it
Then indeed the next time around
I’ll believe you and definitely grasp the day called ‘tomorrow’
Futo ki ga tsukeba yoru
Gekkou ni terashidasare genjitsu ni hikimodosareru
Kiri ga hareru you ni
Watashi wa nani o shiteta n darou
Yomigaeru kioku ni kokoro ga shimetsukerarete
Dou shiyou mo naku kurushikute
Doushite watashi wa kizukanakatta no
Maru de subete ga akumu
Fukai yami no naka
Moshimo yarinaoseru nara
Shinjite asu to iu hi o kanarazu tsukamou