Eren had to admit that Kirito had impressed him. The first moment he saw him, he saw a person who knew what he was doing, even though that person never battled with a titan.
He thought Kirito was just a defenseless little boy who Eren had the instinct since he first met him to protect him at all costs.
"I'm not a baby Eren. I've defeated a world full of monsters, I survived and slayed! I know how to take care of myself." Kirito had told him when Eren followed him on every outside mission, killing titans that got near the boy. And when Eren shifted to a titan, he literally tore apart any titan that was just in the distance of Kirito.
In truth, Eren saw Kirito as the cute small kid that was just in the titan world by mistake.
"I'll make sure you'll go back to the real world." Eren would always say to him at night, when Eren would sneak into Kirito's bunk, and hold him close and tight. Kirito had told him about Sword Art Online, and the real world seemed like a dream to Kirito.
"I'll take you with me too. I'll free everyone in this world. I promise." Kirito would lay his head on Eren's chest, Eren's arms wrapped around him and chin on top of his head.
Eren would smile at Kirito whenever he said that, and would kiss the top of his head, dreaming of what the real world would be with Kirito.
It all happened to fast;
One minute Kirito and Eren and the rest of a squad had successfully killed a titan, and they were celebrating when Eren heard the gasp-
Kirito was struggling against an older taller man with blonde hair, he wore a long green cloak and a crown, his ears were long and pointy, and wore a sick smile.
Eren growled, taking out his sword, his other hand curling into a fist, walking towards them. The man grabbed Kirito by the waist, grinning, and said,
"Say goodbye to your friend forever, I'm taking you back to where we were more comfortable-" Kirito squirmed and punched, kicking but to no avail. The older man grabbed Kirito's arm twisting it. He yelped.
Eren knew Kirito was in pain, he was going back in that birdcage and he couldn't do anything.
"Come any closer and he suffers." The older man still grinned, as if taking pleasure in Kirito's pain. It tore Eren apart.
"Stop! Don't hurt him!" Eren yelled, and Kirito looked at him. He tried to give a small smile, despite the pain.
"Don't worry Eren this won't hurt me-"
"How adorable." The older man tightened his hold and snapped his finger, in a moment they started to fade.
"KIRITO!" Eren yelled, now running.
"Eren! I love you!" Eren felt his heart stop when Kirito said that, his free hand reaching out to him. Eren reached out, and yelled, "I'll find you!"
But Kirito and the man faded completely, only leaving little green shards. Eren grabbed at them frantically, saying over and over, "Kirito! Kirito please come back! I'll find you!" He fell to the ground, and a single green shard fell to his hand.
"Please wait for me. I love you too." Eren said, and tears slipped.
He sobbed uncontrollably as the shard exploded, dissapearing completely. Eren punched the ground, tears flowing.
He cried for not being able to protect his lover, he cried because he might never see him again.
He knew Asuna was going to save Kirito from the older man, Sugou. He knew Asuna would protect Kirito, be with him in bad and good times.
He cried because he wouldn't be with him for a long time and perhaps never again.
And it completely shattered his heart and soul.
"I'll find you. I'll free everyone in this world just like you wanted." Eren said lowly, and slowly got up, swords in both hands.
He patted his jacket pocket, and sure enough, he felt a square thin paper. He pulled it out, and saw the photo of him and Kirito, his arm around his waist, and Kirito smiled shyly at the camera. It had been a free day, spending it inside the walls with for once no worries.
"I promise." He said, clutching the photo, and he carefully folded it, putting it back in his pocket.
He knew he'd find Kirito one day, or die trying to.