I like how 'that's how it was' is so understated.

I like the atmosphere of this song, which feels like looking back on past emotions in a calm manner.
It feels like it tells a story calmly rather than expressing emotions in a flashy way, so I find myself focusing more on the lyrics.
The members' delicate vocals bring out the song's melancholic vibe so well that it leaves a lingering impression the more I listen to it.
If you listen to it during a quiet time, it feels like past memories and recollections naturally come to mind.
If you like DAY6's calm and profound music, this is a song I would recommend.