Okay, I think I get it now - I'm supposed to be replacing the Steel Diver save not the ほぼ日の健康手帳 save. Good thing I realized that after I bought one of the other games and tried (and failed) with that >.< Off to try.
https://3ds.hacks.guide/installing-boot9strap-(seedminer)
Section II says JPN ほぼ日の健康手帳™ users should follow http://steelminer.jisagi.net/ instead of this section. Once those instructions have been completed, resume this guide at “Section III - DSiWare Injection”.
Instruction 1 in your link is...
I'm trying to follow the instructions at 3ds.hacks.guide on a JPN 2ds (11.8) using ほぼ日の健康手帳. So as instructed I'm following http://steelminer.jisagi.net/ but I get stuck at Section IV, because ほぼ日の健康手帳 isn't making a save file on the sd card for me to replace. It's saving on the console only...
Only thing drive me crazy is all these new horror games nowadays is its so dark, all time. I can't even play them. I understand they trying to create spooky but be creative a little, not just darkness with pop out scare scenes.