The Verdict: Not eligible
Japan has no route for descendants beyond the fourth generation, and no religious-return route of any kind. Look at our Skilled Migration and Golden Visa routes for Japan instead.
There is no fifth-generation category, heritage visa or discretionary route for distant ancestry.
Count again from the last person in your line who held Japanese nationality, not from whoever first left Japan. A great-grandparent who emigrated and never naturalised elsewhere stayed Japanese, which can shift everyone below by a generation. The emigrant ancestor's family register (koseki) shows it.