Right away this song feels like it has a strong connection to nature. The idea of chasing fireflies can both put you in your backyard as a kid or out in the middle of the woods, but either way you're outside and it just reminds me of a different time when kids were told to go outside and play until it got dark. There is also probably a real problem with nature right now where the number of fireflies is dropping.
Roslyn Witter channels that specific era of Taylor Swift as this song takes us through a mix of folk, Americana and even a little leaning towards country at times. It just has that wholesome and down to Earth type of feeling you would expect from a song about nature, which though that is in the title there is a deeper meaning there as well.
This music video takes place primarily in the woods and fields- outdoors in nature- as there is sometimes just one person and other times there are two. Visually, this captures the idea behind the song lyrically. The idea of being happy with someone when you're chasing fireflies is to say that you can find joy with them in doing the simplest of things. The way the music video also looks makes it feel as if these are the only two people in the world.
Some people want to be in a relationship for the wrong reasons. Maybe you want a roommate or someone to go to art gallery openings with. Maybe you're just tired of playing basketball by yourself. But when you find that someone that you'll even do nothing with and it can still be fun, that's when you know it's special and that's what this song is telling us here.