風と遊ぶ白いカーテン
kaze to asobu shiroi kaaten
White curtains blowing in the wind
{lit. playing in the wind}

チョークのバブロ・ピカソ
chooku no paburo pikaso
And Pablo Picasso's in chalk
{several of picasso's works are done in chalk}

騒ぐ夢
sawagu yume
Having noisy dreams

ふてくされた黒板消し
futekusareta kokubankeshi
The blackboard eraser became sulky
{as in, the school time's over, the eraser gets used and becomes sulky as to be totally dirty. You'd also be mad}

解放感のチャイム
kaihoukan no chaimu
And the feeling of freedom chimes

走るキミ
hashiru kimi
As you start running

世界は屋上で見渡せた
sekai wa okujou de miwataseta
I looked over the world from the rooftop

そっと心に刻んだ
sotto kokoro ni kizanda
The scribblings of my springtime of life
{or "youth" to keep it simple}

走り書きの青春を
hashirigaki no seishun wo
were slowly carved into my heart

未来の僕は
mirai no boku wa
I wonder how

どんな気持ちで
donna kimochi de
the future me

振り返るのだろう
furikaeru no darou
would look back on them

ずっと心が痛んだ
zutto kokoro ga itanda
All those childish mistakes

子供じみた失敗も
kodomojimeta shippai mo
caused pain in my heart
{or Those childish mistakes  --> always caused pain in my heart}

笑える時が
waraeru toki ga
It'd be nice if the time comes

来るなら良いな
kuru nara ii na
wherein I can laugh.

大人になるのも
otona ni naru no mo
It might not be so bad

悪くないのかも
warukunai no kamo
to become an adult