the montage concept 

Scenes from Sepiatone = memories ] Tamaki and Haruhi are basically "over" if you will. And well they don't know what really went wrong and they slowly start to see how many times they proved their love and risked themselves for the sake of love..? Yes well thats my concept but if you want to see it any different go ahead.

lyrics 

In the night, I am afraid

of dreaming with you,

and this is not only a punishment,

its something i feel, for you.

[pre chorus]

its stupid to think that one day you'll return

and this solitude it kills me more each day

[chorus]

and i don't know what happened and i don't know how i failed

if i gave all my love to you

i don't know what happened and i don't know how i failed

if so many times i risked myself for you

and i don't know what happened

[verse 2]

its difficult to face this crude reality

because you are no longer here

[no longer here]

but inspite of the pain

i must continue which kills me [kills me] without your love

[pre chorus]

its stupid to think that one day you'll return

and this solitude it kills me more each day

[chorus]

and i don't know what happened and i don't know how i failed

if i gave all my love to you

i don't know what happened and i don't know how i failed

if so many times i risked myself for you

[verse 3]

it is certain that life

is not the same without you

and no matter whatever happens

a part of you is with me

and i don't know what happened and i don't know how i failed

if i gave all my love to you

only to you

I want you just for me

I'll never know and never will

and i don't know what happened and i don't know how i failed

if i gave all my love to you

and i don't know what happened

[I don't know how i failed]

well if you aren't here

my love, with you i would just die.