夢心地 describes the floaty, blissful feeling of being immersed in a dream. It is more poetic than simply saying "happy" or "dreaming," making it a memorable expression for learners.
In the song, フワフワと夢心地 captures the singer's feeling of drifting beside the person he loves, so enchanted by their shared moments that reality seems almost unreal.
"いつか" (Someday) is Saucy Dog looking back at a relationship through a pile of tiny, specific memories, and that's what makes it hit. There's no big dramatic breakup scene. Instead you get her lying down on the ground to look at the stars, the two of them sharing ひとつの傘 (one umbrella), sitting on swings, and best of all, the push-button traffic light that she always ran ahead to press: "いつも君が走って押すくだり" (the bit where you always ran and pressed it). The word くだり means a "bit" or "routine", like a running joke between two people, and it's such a sweet detail.
Then the song turns. "信号機は無くなるみたいです" (it seems the traffic light is going away), and right after, the feeling of missing her "いつかは無くなるみたいです" (will someday go away too, it seems). That parallel is quietly brutal. He mentions a snowy day at an empty park in 田和山 (Tawayama, a real place name), where she looked "ちょっと寂しそう" (a little lonely) under a streetlight, and he admits "君を思い出にできる程僕は強くはない" (I'm not strong enough to turn you into a memory). The ending is gentle rather than bitter: a sip of warm cocoa, her smile with "嘘は見当たらない" (no lie to be found), and a casual じゃあね (see ya) with the hope of meeting "またどっか遠くで いつか" (somewhere far away again, someday). Watch for the casual speech here, like 忘れられんなぁ (I just can't forget), a dialect-flavoured way of saying 忘れられないなあ.
Saucy Dog formed in Osaka in November 2013. By 2015 everyone but singer and guitarist Shinya Ishihara had left, and in 2016 bassist Kazuki Akizawa and drummer Yuika Seto joined to make the trio that plays today.
They won the grand prize at the MASH FIGHT! Vol.5 audition and put out their first nationally distributed mini album, Country Road, in May 2017. Their 2021 song Cinderella Boy has passed 540 million streams, which puts it among the most streamed songs in Japan.