The amount of times I see people ask about modifying the saves that are on the SD from installed titles is ridiculous. If you just search the forum you will find that you can not modify the safe without decrypting it, which is impossible unless you either have homebrew to decrypt it from console (using a save manager like JKSM) or I believe it can also be done from computer as well if you dump a certain file using software that has access to arm9, meaning 9.2 or lower firmware or A9LH.
But without any homebrew, the answer is no you can't