secret of my heart

该曲由仓木麻衣本人作词，歌词围绕“不能向任何人透露的秘密”这一主题撰写。为了宣传单曲，唱片公司将该曲作为公司负责原声歌曲的动画《名侦探柯南》的片尾曲^[2]，因而仓木麻衣在创作歌词时将自己的回忆结合了动画中的人物毛利兰的心境。另外，该曲由为仓木麻衣完成前两张单曲的大野爱果、Cybersound分别完成作曲和编曲，音响制作由Perry Geyer、Miguel Sá Pessoa、Michael Africk三者共同完成。

2002年，仓木麻衣发行同名英文专辑，将该曲作为专辑主打曲，并为该曲重新撰写歌词，编曲者更换为ZOD，曲风也因而和原版产生较大区别^[3]。

secret of my heart(8)どんな 言叶に変えて

君に 伝えられるだろう

あれから いくつもの季节が

通り过ぎたけれど

いつも 傍で笑ってる

私にも言えないことが まだ ひとつだけある

Secret of my heart 疑ってもないね

いつだって少しの未来があれば

真実は 手に入れられるはず

I can't say もう少しだけ I'm waiting for a chance

こんな 穏やかな时间

もっと 繋がっていたい

全てを见せるのが 怖くて

少し离れて歩く

君の横颜がなぜか

壊れそうで 守りたい もっと近づきたいよ

Secret of my heart 理解ってくれるよね

谁だって 逃げたい时もあるけど

それだけじゃ 何も始まらない

I'can't say きっと必ず　I'm calling for a chance

Can I tell the truth?　その言叶言えず 空回りする唇に

Feeling in my heart 隠せない これ以上　'Cause I love you

I will be with you Wherever you are Can you fell my heart?

Can't you see,you're my dream 失いたくないよ

大切な 君と过ごすこの时间

あきらめる位なら 信じて

I just wanna say もう迷わない

Can't you see,you're my heart どんな作り物も

简単に壊れてしまう 日が来る

だけどまだ いつまでも変わらない

Secret of my heart Our future is forever^[4]

《名侦探柯南》片尾曲截图(23)我要怎么样改变语言的传达方式

才能传达给你啊

从那时起 不知有多少季节从这里经过

你总是在身旁笑着

对我而言 我也有一件难以启口的事

Secret of my heart 毫无疑问地

不管何时 只要有少许的未来

真实一定能够实现的

I can't say 再一点点 I'm waiting for a chance

像这样平静的时间

希望能更加维系下去

害怕 看清一切

所以稍微保持距离行走着

你的侧脸庞为何

好像快垮掉似的 想保护它 想再更靠近你一点

Secret of my heart 你应该能了解我的心意吧

不管是谁 虽然都有想逃避的时候

但是只是逃避 并不能解决问题

I can't say 一定 I'm calling for a chance

Can I tell the truth？那句话到嘴边了 却无法说出口

Feeling in my heart 我已无法再隐藏下去了 'Cause I love you

I will be with you Whenever you are Can you feel my heart？

Can't you see, you're my dream 不想失去你啊

与你共度的重要时光

相信着绝不放弃

I just wanna say 再也不彷徨了

Can't you see, you're my heart 不管何物

都是轻易就坏掉了 总有坏掉的一天

话虽如此 但无论何时都不会改变的

Secret of my heart Our future is forever

《Secret of my heart》Starlit night above the roof tops

I sit and think, what words

could show you how I feel?

Our happy times were they real?

So I wonder

Shooting star, falls as if to tell a happy end

Will come because you're

by my side always a smile

But all the while, there's still one thing inside,

that I cannot tell you

Secret of my heart,

when can I ever start?

Never any doubt,

knowing how someday

I'll say I love you

It will shine on through,

my love will shine out true

Give a little time,

I'm looking for a sign

You know I'm waiting for my chance

So quiet now, winds whisper true to me

I feel a need, to scream out loud

these things I feel

Celebrate this love

I can't reveal I can't show you

So here we are, together once again

you seem to walk

This little distance from my side

your face it seems so sad

I wonder what you hide

I wanna be close to you

Secret of my heart can

you understand those parts

Hidden far away, in a place

I run to, doesn't everyone

In my heart I know I must let our love grow

I can't say why, I know that

I must find a way to call out for my chance

Can I tell the truth?

No words come to my mind

They escape from my lips to the clouds above

Feeling in my heart, I can't hide,

I can't hide anymore, 'cause I love you

I will be with you Wherever you are

Can you feel my heart?

Can you feel my heart?

Can't you see you're in my heart

but things may break apart

Maybe one day It's difficult to say

how long two hearts can beat as one

But I know now all the same

no change will come unless

I play the game

I just wanna say, I think

I might be ready baby

Can't you see you're in my dreams

I can't lose you baby, see?

Every time we meet every time

we're near boy,

gives all meaning to my life

Baby don't get down, someday

I will come around

Secret of my heart

Our future is forever

Secret of my heart...^[5]

《Secret of my heart》是仓木麻衣的第三张单曲，歌词撰写的十分感人，曲子也很柔情。作曲者大野爱果带有JAZZ气息的音乐与仓木麻衣融合了R&B和POP风格、红酒一般醉人的声音，在麻衣略带神秘的声音里营造起动感的折迭^[6]。歌曲中跳动自如的音符，清澈干净的声线，将悄然带着恋意的少女心情展现出来^[7]。（腾讯网评）

《Secret of my heart》的MV拍摄于涩谷公会堂，拍摄时并未使用相机而是使用了胶片。MV以仓木麻衣独自一人走入会场为开端，当她按下音箱开关时，音乐响起。仓木麻衣面对着没有任何人的观众台上，在舞台上开始一个人演唱。伴随着她的演唱，镜头转向了记载着仓木麻衣一举一动的照片被洗出来的画面，这些照片在歌曲的过门音乐响起后飘在会场的上方。演唱结束后，仓木麻衣关闭音箱，离开了会场。