Translation of "Wane" in Japanese

They say it's on the wane, but it's still got something hasn't it?

落ち目って言うけど、まだイケるよね。

As the moon continues to wane, she must make the most of the blackest nights.

‎月の光が弱まるなか‎― ‎漆黒の闇に勝負をかける