The Words 'best Friend' Become Redefined lyrics by Chiodos

I believe the song is about him being in love with his best friend, but they can’t be together for whatever reason. He doesn’t understand why they can’t be, so he does something horrible to her (possibly killed her). Now he regrets it so he cuts himself off from the outside world.

“I've been hiding in this bed for weeks from this”
This is his situation after the events of this song. He is depressed and isolating himself from the world.

”Throats raw from screaming and I haven't said a word”
He has told her over and over that he wants to be with her, but she doesn’t understand. Since she doesn’t understand, it’s as if he hasn’t said anything at all.

”The sky is calling, and the stars they point to this”
He truly believes that she and him are meant to be.

”To a chair we see your breath in the air, but only for a little while”
His love isn’t unrequited. It’s just forbidden. They can’t be together for whatever reason, but they have hooked up a couple of times before.

”Your cold pale skin and tainted purple lips“
The girl he is in love with has been with many guys before. She has been hurt, so now she is afraid. Thus, her skin is cold and pale. Since she has been around with other guys her lips are tainted. But they have also become purple (as in swollen) because these previous guys have really hurt her.

”Let me embrace you with this kiss”
He really wants to be with her no matter what, even if it hurts her. If you kiss someone who has swollen lips, then it’s only going to hurt them. This “kiss” could refer to something he did to her out of anger. He might have killed her because they couldn’t be together in this world.

”And together we'll float like angels. Together ... together we will float, like angels”
He wants to be with her in the afterlife since their love is forbidden in their current life.

”Higher than the heavens the clouds part ways”
He believes that their love could strive if she forgives him for all that he has done to hurt her.

”Promise me to never look down! and we'll stay like this forever”
If she forgets about the past, then he believes that their love will last forever.

”If your stomach feels weak than my work here is done”
He believes that the only way to get her to understand how strongly he feels is by hurting her, just as she has hurt him.

”To hide from our twisted ways, I've been hiding in this bed, been hiding in this bed for weeks”
He now regrets everything he has done. He has lost her forever and any chance of ever being with her. So now he is isolating himself from everything because he no longer knows what to do.

This interpretation is almost exactly what I went through with my best friend. But don’t worry, I didn’t kill her. I just hurt her emotionally really bad. She has already been hurt in the past by a previous boyfriend, and I added to that pain. So my interpretation may be a little biased.