i think it's about a real friend, a best friend, who he spends all his time with. they're inseparable and they fit so perfectly with each other that they're almost separated from the world with their "secret codes" that nobody can hear. as time goes on, real love substitutes platonic love. he "can't pretend"..."i can't see you anymore"...signifies how he can't pretend to just be friends anymore and the only way he can get over her is to stop seeing her.
i think it's about a real friend, a best friend, who he spends all his time with. they're inseparable and they fit so perfectly with each other that they're almost separated from the world with their "secret codes" that nobody can hear. as time goes on, real love substitutes platonic love. he "can't pretend"..."i can't see you anymore"...signifies how he can't pretend to just be friends anymore and the only way he can get over her is to stop seeing her.