I noticed something interesting after doing that third option. Different version of same character may shares EXP/level, however they have separate equipment slot. Now I understand why I lost the knife when I didn't deequip Akemi before she changed outfit in the beginning of the game.
I realized it when they switched to another outfit, their equipped stuff in main outfit are all not available and when they switched back to main outfit, their equipped stuff in alternate outfit are not available. So when choosing third option for second time, I used this opportunity to strip every stuff when they wore alternate outfit once more. And just like I thought, stuff found in that correspondent dungeon are now available when they are back in main outfit again. Turned out some stuff give better stat than their current gear.
I also tested it to make sure by reloading my beginning save. If I had removed her Headband when she still wore JK outfit, there will be another copy of Headband after changing to her armor. So Headband in her JK self is not the "same" one from her armor self.
This applied to that other person as well which "changed" after that very same event, so make sure to strip everything before choosing third option for second time then reequip those removed stuff afterward.
I realized it when they switched to another outfit, their equipped stuff in main outfit are all not available and when they switched back to main outfit, their equipped stuff in alternate outfit are not available. So when choosing third option for second time, I used this opportunity to strip every stuff when they wore alternate outfit once more. And just like I thought, stuff found in that correspondent dungeon are now available when they are back in main outfit again. Turned out some stuff give better stat than their current gear.
I also tested it to make sure by reloading my beginning save. If I had removed her Headband when she still wore JK outfit, there will be another copy of Headband after changing to her armor. So Headband in her JK self is not the "same" one from her armor self.
This applied to that other person as well which "changed" after that very same event, so make sure to strip everything before choosing third option for second time then reequip those removed stuff afterward.