Half Japanese sister

hi, I have a Japanese sister who is turning 16 this October. She is currently living with his japanese father who is married to my mom. However our mom passed away 4 years ago. Our Japanese step dad won't let us see our sister and do not want to give us the privilege to take good care of her. Can my sister can sponsor me or at least the Japan government will give us the chance to at least be with my sister and be able to take good care of her. We know that his dad is old enough and base to my sister she was living as if she is at her own. Because her dad can't take care of him because of his age and illness. Please help.

You can try contacting the city hall of the city she lives in, and show your concerns. The city may not be able to let you see her, but they can do things to make sure she is okay. If you could share with us what city she lives in, someone may be able to provide you the contact info.