Tsuma no Nakami wa Kodomo no Mamadatta Nodearu.

Synopsis

It's suppose to be an innocent newlywed life, but there is a big problem. My wife, who still has the mind of a child, doesn't know anything about adult matters! Even though we're husband and wife, I can't force her to do it, and I don't know how to explain it to her... Look at how they're jiggling all over the place! The unintentional teasing from my innocent young wife is going to drive me mad! (Source: ComicWalker, translated)