This game often backups hero structs. And, if a hero struct has wrong checksum/CRC, the game restores it from the backup.
I crafted a fake backup struct on SRAM (with z3 solver), and created an amulet by changing name.
On Famicom version, the game displays a logo every time you reset, so this movie is not so fast. If this save glitch can be executed on NES version, it will be quite fast. But, it might be more difficult to execute this on NES version, because you can use fewer character kinds for a hero name.