Need a mom chair from Japan identity maker or designer  

Autocorrect strikes again!

This kind of shape is often called a scoop chair, so you might find it by using that as a keyword. I didn't see anything in a few pages of image search results but it might be there.
There might also be some Japanese boards dedicated to design; if it is a chair that was not made for export, someone in Japan may know more about it.
I clicked on this thread because of the "mom chair" in the title---a good friend in Denmark told me that they all call 50's and 60's teak frame lounge "mother chairs", because everyone's mother has one" - ! He told me that when I found one for $13 in a thrift store in the little town where we lived. My daughter has it now and it will always be The Mother Chair. It's completely different from the OP's chair, though.