You may use this card to return Fusion Monsters with no effects to the Fusion Deck.
If you have 4 Effect Monsters and 1 Normal Monster with 1500 ATK in your Graveyard, you can activate this card and return the 1 Normal Monster to your hand.
If you have 5 Normal Monsters in your Graveyard, you can activate “Backup Soldier” and chain a second “Backup Soldier” before the first resolves, because the 5 monster requirement only needs to be fulfilled at activation. This would allow you to put all 5 monsters in your hand, 3 with the first “Backup Soldier” and 2 with the second.
If your opponent activates “Delinquent Duo” and you chain “Backup Soldier” with 2 pieces of Exodia and retrieve the other 3 from your Graveyard you win the Duel before you have to discard for “Delinquent Duo”. This is because you check for victory conditions in between steps in a chain, (but not in between two separate effects of a single card like “Graceful Charity”).