First of all, he must not be from Neiguang class, because Neiguang class will not transplant sharingan, so this masked man must be a powerful medical ninja. When Ben's brother transplanted the kaleidoscope, it was probably this masked man who transplanted it. The reincarnated group said, "This boy Nagato has made progress. He was resurrected through reincarnation, so I think this Nagato should refer to the masked man instead of six Nagato.