Please don't use the word
"retarded" when referring to people who are slower in anything than what we considered mainstream. The word retarded is no longer use as it is disrespectful towards people who are slower in general. The correct term to use now a day is " disabled ". This is respectful language as we all should learn how to use correct terms.
I don't think this character is even necessarily developmentally delayed so much as deprived of an education, even the basic speech acquisition most kids get in their early years. Earlier people were comparing him to the "Wild Child" Genie and I agree. See
https://www.youtube.com/watch?v=hmdycJQi4QA
I doubt you will ever see this because it doesn't seem like you are a registered member but just to educate you more and point out your lack of education the word 'disable' isn't any better. Call someone disable when they don't considered themselves 'disable' and you'll get a load of shits shot at you. If ever talk about a real human and not some 2D characters on some scanned papers online then I would have used the word "academically challenged" rather then the word 'disable' or 'retarded' to described them. YOU SPEND YOUR LIFE TOO MUCH ONLINE THAT YOU MAKE YOURSELF A 2D CHARACTER OR WHAT? ┑( ̄Д  ̄)┍
Holy shit, the postman is the second daddy. he's gonna start licking he retarded kid *forgot his name* and die a death like the daddy. the retarded kid seems to be evil if u look at chapter 1 it seems like he's kind of old already but when the dark-hair uke grow up they look about the same age? is the retarded kid some kind of immortal monster...well, i guess it's pretty obvious the retarded kid is the monster mantis killing anyone how have sex with him so farewell postman for u r gonna fall pray to the mantis like the daddy who die in the earlier chapter. and isn't that postman the same postman from chap 1 during the funeral, i can see the 2 moles on the chin.
i think i will wait until this manga end to come back since manga like this just make me wanna do the levi kick on annoying characters. though i am amazed that in 4 chaps we have yet to see any anal sex...only some licking and hand jobs.