* Break it down: The riddle plays with words and relationships.
* Focus on the key words: "Little Japanese" and "big son" suggest we're talking about a family member.
* Think about family relationships: A "little Japanese" might be a small child. A "big son" could be an adult son.
* Consider the final phrase: "The not father" eliminates the father.
Solution: The answer is mother.
Here's why:
* A "little Japanese" refers to a young child.
* A "big son" is an adult son.
* The mother is the one who is "not father" but still a parent to both the child and the grown son.