[Mitkki]

Thanks for your efforts as always.
Just a few comments with my preferences.

Originally Posted by masa

Actually, you had long been crying in your heart, hadn't you?
But you were hiding it, that's what you haven't changed in

I feel that 'have' would be more appropriate than 'had' in this case. 'Had' is usually used in conjunction with another clause and emphasizes the termination of a prior clause; eg. I had been crying, but I stopped.
I'd prefer something like: Within your heart, you've actually been crying for a while haven't you? But you were hiding it. That part of you hasn't changed.

We always knew, we have never had a day where we forgot.

'We always knew that we've never had a day we forgot' seems more natural for me. Though I would prefer something like: We always knew there hasn't been a day we've forgotten.

I know painfully, your feelings are reaching me without change
Because our promise that we would share everything is not a lie at all

'I know (painfully)/(to a painful extent) that your feelings are reaching me unchanged, because our promise to share everything isn't a lie at all' would be my preference.