It's about Eunji, 8 years old girl, who is battling with brain cancer stage 4 and a big fan of Treasure. Her big sister, Y/N was ready to do anything for her little sister. all she wanted is her little sister's happiness. 

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걱정 마, 한 번 더 뜨겁게 웃어줘 (ay, 뜨겁게, oh)
웃을 때 더 예뻐 넌
힘을 내, 우린 결국 빛날 테니 (ay, 감은 눈을 떠, oh)
You're the only one treasure

(Don't worry
Smile at me warmly once more
Ayy, with passion, oh
You're prettier when you smile
Cheer up
We will eventually shine light
Ayy, open your eyes, oh
You're the only one treasure)

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