User blog comment:Stone Roger/Natsu and Zeref have somekind of relation?/@comment-180.191.65.238-20141223100550/@comment-70.193.51.34-20150125192232

I wouldn't say the scarf seals him, because his scarf has fallen off before and I'm sure he takes it off to at least wash is. Maybe some different seal though, maybe Natsu him self reading the book is the seal.