I posted it on AO3, but you can also find it on Fanfiction.net and Wattpad. The name is "Never give up without a fight".

Here is an excerpt from the first chapter:

In, Out; Deep, Slow ... Miyuki tried to calm his hectic breathing, while at the same time using his whole body control to hide the pain in his chest. Only this inning, he could make it. Now it was about somehow getting his act together. They needed the points. He had to return to the home plate, then they would be in the lead and the dream of Kōshien could become reality. The last few meters where longer than the entire distance to the third base. Each breath was accompanied by a wheezing from somewhere deep inside his chest. I must go on, was all he thought. If he were to give up now, then everything was for nothing. This one point could decide everything. He could decide everything. Therefore, he ran, even though he felt that there was no oxygen in his lungs. He ran, though his field of vision was blurred. Only a few meters ...

„Back Home!“

Miyuki knew time was running against him. He wished his legs would carry him faster. That he was one of the fast runners of Seido. He wished that not every breath would be such a pain. Only a few meters were left.

„Akiba!“

He threw himself forward and stretched his left arm out to the home plate. When his body hit the ground, he felt the last air escape from his lungs. Every movement, every breath was accompanied by a renewed surge of agony. He was desperately fighting for air. Why was there no oxygen?

"Safe. 5-4! Seido has managed to turn the game into his favor!"

Why did he feel as if his chest would burst? He couldn’t give up yet. He still had to play the second half of the inning. It was not over yet. They had not reached the goal yet. He gritted his teeth until his jaw hurt. Once again he made the desperate attempt to hide the pain. He wanted to get up, but his legs didn’t provide the necessary power, and he was panting on all fours for air. Panic flooded his veins. No, that couldn’t be the end. He still had to play the second half. He was the captain, the team needed him! All he had to do was hold on for a few minutes. They were so close ... so close to everything. Miyuki made another attempt, but his legs didn't obey him. At the same time, he felt like a fish on the dry. He didn’t want to breathe anymore, because the pain that went through his chest every time he did was too big. How much time had passed since he made it back to the Home Plate? Minutes or just a few seconds. He only knew he had to get up if he didn’t want the team to worry. They were so close to the championships, that he couldn’t risk the team giving it away just because they were worried about him. The focus had to be on the game and only on it... Come on, get up. Stand up! His right hand clenched into a fist and he struck the sandy ground repeatedly. The pain pounded in his whole body and disturbed him intensely. He couldn’t think.

„Hey, Mi-“

Far away, he heard Shirasu's voice.  All he could think of was the team. The championships, their common goal. He didn’t know how, but he brought the strength to lift his upper body and stretch his fist in the air.  Shortly thereafter, he heard a cheer that echoed through the stadium.  Miyuki saw his teammates in the eyes and thought he could see relief in it. It was for the best, he thought, Shirasu had to concentrate on the game. They were in the lead, but it wasn't over yet. A counter-attack could still be made. This wasn't the time to rest. With all of his self-control, Miyuki finally managed to get his tortured body into a standing position. He high-fived Shirasu and jogged to the dugout. His legs felt heavy, and the frightening feeling in his chest had not subsided. He had the desire to cough, but suppressed the reflex, when his eyes met the coach. Miyuki tried to put on his smile and nodded to Kataoka, when he slowly descended the stairs.

"Miyuki, strong run!" Kuramochi's loud voice echoed in his ears. Shortly afterwards he felt a new wave of pain spreading from his shoulder throughout his whole body after Kuramochi had given him a light slap. He could't avoid a lightly moan. His legs threatened to give way, but something or someone held him upright. "We're going to change our undershirts!", he heard his friend say and let himself be carried into the cabin. He no longer had the strength to resist Kuramochi. Shortly thereafter, the shortstop made him sit down on the bench. "Don't you think Ono should take over now? You are sweaty and can hardly stand on your feet ... " Miyuki jumped up quickly. He could play! He had to prevent that in this crucial phase the focus of the team being destroyed by the concern for him. He was the captain, he had to prove fighting spirit. However, all of a sudden all the strength left him. He felt an unbearable hot pain in his chest and a metallic taste on his tongue.

His body fell forward, but he didn’t land on the ground, as Kuramochi caught him. He felt his breathing became more hectic. He panicked, as suddenly, there was no air left in his lungs. His head lay limp on the shoulder of his friend. "Kuramochi," he whispered softly, "I'm sorry, I couldn’t keep the promise."