Makoto hates the water. That's almost a given fact. He doesn't really know why he bothers with sticking to the water so closely, but he does. Every time he dives into the pool, his heartbeat races—not of excitement, but fear. Fear that something will happen again, like it did years ago. He hates the water not because of some previously established thread, but because of fear. He fears the water only because it will end up consuming him, like it did before.
He doesn't say it, but he's deathly afraid of repeating the same incident when he was younger. He learns to be cautious, and hence, the backstroke. He keeps his face up, out of the water—it's a sign of hope, some kind of salvation for him in case anything happened again.
Seeing Rei jump in headfirst that one time made his heart stop. It reminded him of himself. A little too much. And when Haruka dived in to save the younger male, he felt relief.
Makoto wants to reconcile, but somehow, that barrier gets in the way. Ever since his near-death experience with water, he vowed never to touch a single body of water. Yet, when Haruka persuaded him to swim again, and taught him to accept the water's presence, he leaned to cope with survival. He knew how to swim from a young age, but somehow, learning the ferocity of the water and its torrents, the open sea and its vicious cycles, Makoto understands that perhaps, Haruka is more accepting to water than he is. He understands that properly now—Haruka is like a fish. Makoto will never be because he will never accept and break through the barrier of fear.
Because he had died once.
Or he would have, if Haruka didn't dive in to save him at the last moment. That's all he heard, unfortunately, because since that moment, everything prior to that has been absolutely hazy, and no matter how many times he tries to remember, he can't. When he had cut off his oxygen supply that one time, and the delayed rescue had already decided the boy's fate.
Makoto had suffered severely because of that. The fear settled in for both their parents, especially Makoto's, because it was Makoto lying on the hospital bed, with the oxygen mask attached to the boy and not Haruka. Makoto was the one dying, not Haruka. It was Makoto's life, not anyone else's. So after ten days spent in the hospital, the green eyes fluttered open, and finally, the boy was brought back.
But it had only been temporary, because the first words he spoke was:
"Who are you?"
Perhaps it had been fate, because Haruka was there, right in front of him, and he doesn't know the name of his best friend. It was a cruel fate placed, and Haruka patiently told Makoto about his surroundings. All while holding in the worst feeling a friend could hold. Bitter sadness. His best friend had suffered from amnesia. The doctors said that the memory loss would be temporary, but pain instilled inside of Haruka would not fade.
Maybe he shouldn't have called Makoto out that day.
So, Makoto learned, the fear paralyzed the boy, causing him to miss much of his school year. He was told to repeat the year, and he agreed—it was for the best. That way, he would be together with Haruka. And Haruka felt guilt for the first time in his life.