おあずけ is an expressive word meaning being made to wait for something you want, or having it temporarily withheld. In the lyric "今日のナイターもおあずけだ," the singer playfully says tonight’s baseball game is put on hold because the rainbow is so spectacular, giving this everyday expression a charming poetic twist.
This is a tiny, happy song about the few minutes right after a summer storm. THE BLUE HEARTS were famous for loud, fast punk, but here they slow down and just look around. The first line sets the scene: "雨上がりの夏の夕暮れ" (a summer evening after the rain). Then comes the best simile in the song, "まるでサイダーそのままサイダー" (just like soda, exactly like soda). In Japan, サイダー (saidā) is not apple cider. It is a clear, fizzy lemon-lime soda, so the whole evening feels cool and bubbly.
The details are small and specific. A friend with a "日焼けした顔" (sunburned face) is told to smile, and the puddles hold "宝物" (treasure). The sky is a "水彩画" (watercolor painting) smudged by "風の筆さばき" (the wind's brushwork). The singer feels like he "found something he'd lost", and admits that a rainbow on top of all this would be too much: "世界は止まってしまうだろう" (the world would probably just stop). The one bit of bad news is funny: "今日のナイターもおあずけだ" (tonight's night game is called off too). ナイター is Japanese-made English for a night baseball game, and おあずけ means something you want that has to wait. The song ends on "照れたお日様" (the shy sun) throwing a long shadow, a sweet way to describe a sunset.