OP - Kizuato (キヅアト)

Source: Crunchyroll
Everything that you left behind
Became my everything
The wound pierced into my heart
Still remains as the days continue to go by
If I were to forcibly take it out,
 the pain would never end
So I'll just leave it there
Rainy, sunny, and cloudy days
Spring, summer, fall, and winter
365 days a year
You're there in all of them
Reach in deep
And while you're at it,
 take away my memories, too
The voices that can't be heard
Are strangling me again
Dig deep
And look at the pain within me
Everything that you left behind
Became my everything
Everything that you left behind
Became my life