I like "Happy Days" because of its warm yet wistful atmosphere.

The lyrics that make me look back on the past linger in my heart.
The melody is soft, so it is comfortable to listen to.
It is a song that evokes both fond memories and a sense of wistfulness.
DAY6's signature emotional band sound is charming.
Listening to it makes me think of precious moments from the past.
It is a song that leaves a lasting impression until the very end.