極彩、嬋娟ノ魚。 (Gokusai, Senken no Sakana.)

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Beatiful, you are, absolutely, beautiful. The song seems to be slightly inspired by the story of Orihime and Hikoboshi.

A "fish" falls in love with a man beyond the milky way. She wants to go to him and starts swimming across, but the sharps stars scrape her scales off, killing her.