《笑容無限》的詞曲由日本音樂人宇多田光所創作，中英文歌詞如下所示：
中文詞：
明天還有未到達的地方
眼前只有我和你的目光
天空很亮
彩虹藏在了哪裏呢
沿途的小風光不能放過
願我們
笑得無限無盡的笑著
謝謝老天給了我這麼多的好與壞
風浪中還有你陪我著我
笑得無限永遠的唱著
今天的日子一定要熱烈點過去
總有種感情在心底萌發著
請把陽光盡情灑下吧
微笑地迎向太陽吧
英文詞：
There's a tomorrow with a place yet to be reached
In front of me, only your gaze and me
The sky is bright, where's the rainbow hiding?
Stopping by, let's not miss any scenery along the way.
May we smile endlessly, laughing heartily.
Thank the heavens for all the good and bad they've sent my way,
With you by my side through the storms,
May we smile endlessly, singing forever.
Today, let's make sure this day is lived passionately.
There's always a feeling growing deep within me,
Please, let the sunshine pour down, smile towards it.