Supplemental canon material
Translated by hikari318 , here.
5th(Sync): more agile than the original, but so far the worst in terms of 7th Fonon
Apparently Luke was unable to do anything when he was born, not even chew. The Ion replicas were all created with these basic functions and were even capable of speech.
Mohs ordered the others to be left by themselves in Mt Zaleho (they'd disappear as soon as they die anyway), but the guys who brought them there threw them in the crater and were pretty cruel about it. None of them died immediately, but I'll go into details later.
Everyone (except maybe Ahmed [the lead scientist] but he didn't voice his thoughts) treated them like they really were nothing more than disposable objects.
Got this name from Van because the first time they met, he kept repeating a sentence Van had said ("The synchro level is the problem").
Was more or less aware of what was happening when the guys kicked the other replicas in the crater, so he let them throw him and took the first chance to hide under a rock. That's where Van found him (what was he doing there anyway? Make sure they really disappeared?). Anyway, he took him away, placed some kind of fonic glyph or whatever on his body (to allow him to use the 7th Fonon or something?) and decided to train him. Basically.
Anyway, back to Sync when he was found. He was hot and hurt and the glyph hurt too. He started to develop emotions - pain, sorrow and anger, but didn't know how to express them, so he just went along with Van.
He wanted to look at the other boys one last time, but eventually gave up. They would disappear soon, and were probably better off than him. Climbing the slope when Van called him had been a mistake. When he realized that, jealousy and regrets appeared on his face once more.
Van kept him in a shed in the woods outside of Daath, and started training him in combat, with the hope of making him his subordinate in the Order later. Sync didn't necessarily dislike this training (and everything Van's done for him so far), but he didn't see the point - he was born to replace the Fon Master, after all, so why did he have to train and learn artes?
'It is true that another replica than you will take Ion's place, but I do not think that his life will be better. Even if he will revered as the Fon Master, everything will be decided for him - he will be nothing more than a puppet. On top of that, he will have many enemies. This isn't freedom.'
'...Freedom?'
Sunlight was piercing through the sky and glimmering on Sync's mask.
'Yeah, I may be under restrictions, but I'm more free than the seventh Ion. But what does that change? Don't try glossing things over. You're only trying to use me as you please.'
Van's eyes twinkled.
'I am putting your potential into practice. If you don't like it, you can go back to Mt. Zaleho. If you want to hate something, hate the Score that brought you to life.'
'...Yeah. I think I'll do that,' Sync sarcastically replied. 'I'm free. You've gone out of your way to acquire me, but it's still up to me whether I live or not.'
Impossible!, Van wanted to shout. A replica would consider suicide...? I never thought of the possibility. Seems we should have programmed them so that they avoid self harm.
His having picked up the boy at Mt. Zaleho brought him satisfaction again. With him, he could learn more about replicas than he would ever be able to with Luke.
But Sync, I will not let you die until I can no longer see value in you. You can throw yourself to the depths of the earth all you want, I will always come and pick you up.
Van then tells him how he hates the Score as well, and this peaks Sync's interest.
Some time later, Van shows him the seventh replica and how he is treated, and Sync starts feeling jealous of him. He can't help but notice the nice bedroom, the fine clothes, the respect with which he is addressed to. He wonders how they can be so different when they were created from the same data source.
What's so different between us? I'm the fifth, he's the seventh... I was born first! Why didn't they choose me?!
He felt he was becoming mad with jealousy. He hit the bed's wooden frame, kicked the chair, and, lastly, flung off his mask. Trembling with rage, he traced the outline of his face with his fingers.
'We have... the same face... If you don't need me, don't keep me alive!'
As his fingers slid on his cheeks, he recalled the scene in the chapel.
'Arietta protects the Fon Master, and is protected by her monsters...'
Sync believed that people spent their lives creating bonds with others by protecting them and being protected in return.
No one protects me, and I have no one to protect. I don't have any bond with anyone.
He was just alive, completely excluded from this circle called the world. No one truly needed him. He had no place to call his own.
Sync couldn't forgive the ones who created him. They may blame it on the Score, but it is humans who rely on the Score the most.
Who should I take revenge on, then?!
Sync cried and cursed his foolish existence, that held no hope for a future.
He knows that Van is just using him, but he doesn't really care. He muses that it must be the same for the other God Generals; that they all were attracted by Van's strong resolve.
Sync always toyed with the idea of appearing before Ion without his mask to see his reaction. When he finally did in the core, he let out what he had been thinking the whole time, even though he had promised himself not to do it. He also wondered as he jumped if Van would allow him to die this time, or if he would come to pick him up like before.
Van did indeed bring him back, but in the end, he eventually got his chance to go once and for all.
Everything will disappear... Doesn't that fit me, Van? I'm grateful that you gave me a chance to take revenge on the world, but... but I don't care anymore about what's going to happen next. I have finally won this instant. Me, who had only kept losing until now...