Visa for Japan??? Please Help?

I would be moving to Japan this summer to live with my grandpa. All I know is that I would be living in Fukuoka prefecture and that I would be graduating around there. I was looking at visa options and though Dependable Visa would be good but I wasn't sure about the requirements. Would I qualify even if I'm a grandchild not his child? And yes we're blood related. Thank you soooooo much to all who read this and even more to those who answered. Thanks!