Note: the MC watched only the first Season of AOT before his death ( I mean an MC that knows everything will limit from what I can do).
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After activating his Titan power, Ace did some training, he Discovered that he can use his hardening Ability on other things not just himself alone, he went to the kitchen and got a knife and used his ability on it, for his first time the knife just turned to a ball of crystal and lost it shape, ' I can use it to hit someone in the head', Ace continued to practice for countless time, only to succeeded after 1 month, he is now able to cover his knife with a very thin layer of his hard crystal, not only the knife is almost unbreakable, it became more sharper ' Good now I can use this on the blades that used in killing the titans'.
his days continued with a normal and calm pace, he and Erin and Armin are spending their days playing and talking about their dreams, Armin wanted to see the Ocean, he said that he read a book about the outside world ' Did you know, the Ocean is so large that you can't see its end...the book said it full of salt" his eyes were shining as he talked about it, Eren too had interest in the outside world, he interest kept on growing each days, until he said to Ace and Armin that he will join The Survey Corps, his words mad Armin terrified " Are you crazy, there are Titans outside the wall, the chance of you coming back alive is less than 20℅" said Armin as he told Eren about the danger of the titans, but who was telling that to " I prefer to day in the hands of titans than die here like a caged bird" said the Suicidal Bastard.
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[After 4 years]
Ace and the rest are 9 year old now, The day that Ace was waiting for until now has come.
while Ace,Eren and Armin are playing in front of Eren's house, Grisha came from inside and said " Hey boys, tomorrow I am going to visit someone, do you want to accompany me"
When they heard him their Responses were different, Eren said " Ah!? I don't want to"
while Armin said " I am sorry, my Grandpa needs my help tomorrow "
Only Ace was the excited one of them all, he went and put his hand around Eren and said " oi Eren lets go together tomorrow "
" I said I don't want to" said Eren a with an irritated tone
Ace didn't like the Answer, so he put force in his hand around Eren's neck choking him " Eren... don't ruin this for me...I said let's go"
Eren couldn't breath so he gave and said " o-okay, just let me go"
"thank you...besides we always play in the same spot, we need to go see other places from time to time " said Ace, pretending that he didn't try to kill Eren just now.
seeing that Eren and Ace will go with him Grisha said " Good, we will go tomorrow morning. I am sure you will like the area there"
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[Tomorrow]
Ace, Eren and Grisha departed in the early morning, and their destination is the ackerman's Household...