After those years of Natsume and his missions, you finally understood his pain. Silently, in the shadows, you began those dreadful things in order to lessen his burden. It's not as if you had a choice in the first place, because Persona forced you to. You didn't put up a fight, or even struggle, because you knew you didn't stand a chance.
You can at least keep it a secret from the others. They have no need to get involved. What they don't know can't possibly hurt them.
You aren't the careful type. Any moment now, you might just leak your secret out unknowingly. And so, you tire yourself by telling yourself to be careful every step of the way, never failing to set up the nullification barrier around you and your mind. You made up fake excuses Persona supplied you just to skip class for those missions. You know you are drifting further apart from them, but you kept at your pitiful outer facade that Hotaru knew so well. She didn't guess, much less the others.
Inside, your heart was roaring with the pain Natsume knew. The pain of causing damage to others. The pain of knowing you've rotted to black and had been deceiving your friends all along.
Your friends.
You did slip up. That time you ended up at the hospital for surgery, you were absent for an entire fortnight. Yuu knew where to find you, and so the group trooped there and got a total shock, seeing you equipped with an oxygen mask with several needles stuck into your hands. You couldn't move, because Persona wouldn't risk an escape from you, and had threatened to take away the people most important to you.
When you got back to class, the lie you've spent two weeks thinking about smoothly laid itself out. "I was climbing a tree when i fell accidentally, therefore causing damage to my ribcage. Don't worry, it doesn't hurt me in the very least," You flashed your award-winning smile, and made sure that no one saw you wincing in pain.
No one, or so you thought. You slipped up again like the clumsy person you are, and a few times, Natsume saw through you. At night, while you were returning to your room, he was there, holding you firmly against your own door, demanding to know why you've lied.
You should have known.
He was broken enough. With your heart squeezing so tightly because of regret, you said, "Natsume, please let me go," before opening and then shutting the door in his face. Inside, you sob openly on the stone floor, leaning against the door for support. His shadow never disappeared from beneath, and with you and him so close, yet separated from the wooden material, you fell asleep, into despair and agony.