My son is born in manila but his father is a japanese citizen ..we have to go back in japan but i need to know?

Question:

about the requirements of a 4month old baby for the japanese passport..

Answer:

You or he should have registered his birth within 3 months if they wanted to give your child Japanese citizenship. But I think there is something you can do now.

In fact, it's not clear if you want to give your child Japanese citizenship, or just want him to stay in Japan for a while. So there is no accurate answer.