Moodswinger's Manga

I know that in a story there is no question like something phrase but in this the mc is 25 year old in 4 year old body ..... Ok so the present people know him as 4 year old he isn't even in elementary school so how can everyone assume that he can read everything and understand it even he is a genius....
I like this manhwa but I just can't..... can't why is all the grown up blind.
Even as an adult I can't read a script fully even to understand it thoroughly.
I was just frustrated but I just wanted to vent.
Thank you