海原(うなばら) is a poetic word for the wide, open sea, evoking an endless expanse rather than simply a body of water. In the song, the speaker breaks away from a calm, routine life and comes alone into the ocean, making 海原 a memorable symbol of freedom, risk, and starting anew.
Spitz take a love song and make it all about thread. The title, 見知らぬ糸 (threads I've never seen), sets it up: two strangers' lives get tangled, and instead of a mess you end up with something new.
It opens on taste and memory. Something ブルーベリーみたいに甘い (sweet like blueberries) is so vivid it still has flavour 夢でも (even in a dream), and a memory that should wash away under the waves just won't. Then the speaker admits 迷い込んだんだ いつの間にか (I wandered in before I knew it), and asks the other person if they still haven't noticed that fate has already started, even if they feel out of place. I love how casual that sounds. Falling for someone here is less a big moment and more drifting into the wrong room and deciding to stay.
The chorus is the heart of it: the unfamiliar threads 絡まり新しい色に (tangle into a new colour), get 編まれて (knitted together), and become a 薄い衣 (thin garment) that wraps the singer up. Learner tip: 編む means to knit or weave, so the love is literally being stitched into clothing.
The second verse is the bravest part. The singer used to be 飼われた魚のように (like a kept fish), waiting for food in a calm routine, and then jumped out and swam the open sea alone. There's a cheeky line too: ペテンでも構わない (I don't even mind if it's a con). ペテン is an old-fashioned word for a swindle or trick, and saying you'd accept being fooled is a bit much, in the best way. By the end the singer feels 少し強くなれる (I can get a little stronger), which is a very Spitz kind of happy ending: modest, warm, and wrapped in a soft new layer.