Aito read the letter 5 more times, as if he was trying to commit Ryu's words to memory. He could feel the love Ryu had for him flowing from the paper directly into his fingertips, his veins, etching onto his very skin.
He knew what Ryu was suffering from. It was the trauma of his fake death and he went years without treatment. It was bound to affect him, to cloud his judgement and make him act irrationally. It made him develop a deep longing to see Aito, to hold him and reassure himself that Aito was real. It was like dancing between a nightmare and reality, not knowing which one was true. If he didn't get help, he might end up doing things he'd regret.
After witnessing Ryu's panic attack, Aito understood completely. He understood why Ryu was always so needy and so clingy. If he didn't do something about it, it would get to a time where Aito would not be given any breathing space and that wouldn't be a healthy relationship anymore.