Is there an opportunity for us in Japan?

Hi there,

My name is joed, i don't know where to start or where i can ask for help, i'm 27 years old and my sister is is already 25 years old. Our japanese father left us when i was 2 years old, and my mom is a filipina. My mom wont give me any details of where my father is and she believed that my japanese father is already died. I'm still hoping for us if we still have a better opportunity in japan. Our birth certificate which is the original was replace by a fake one. What happen is that our birth certificate has been processed as late register that is why the surname that we are using is my mom's surname. What else i can do to prove that me and my sister has a japanese blood. Thank you in advance for the answer.