Does Immigration accepts child guardianship?

I am taking care of a child since his birth. He is the son of my wife's sister. The mother has given us the custody of the child. The father can no longer be found, presumed dead together with the rest of the family in Syria. Me and my wife raised the child since birth until now. The child is already 9 years old. The child recognized us as his parents although the he is bearing the surname of his mother. I would like to take the child with me here in Japan. Does Japan Immigration accepts child guardianship in Philippines so that I can bring with me the child in my care? Thank you.

This is something that you should probably contact an immigration lawyer about.

How to contact an Immigration Lawyer in Japan to inquire if child guardianship is accepted in my case?

I'm not sure why you're asking the same question. We're not lawyers here on this forum. Your best bet as mentioned would be to contact a lawyer who knows the process of what to do. You can literally just do a Google search and find information.