The opponent's monster does not have to be destroyed by battle. You can destroy it with "Shield Crush" or "Nobleman of Crossout", and then activate this card. If you destroy all your opponent's monsters, then you can perform two direct attacks.
You can also combine it with "Enemy Controller" to turn a monster into defense and them gain the 2nd hit.
If you have a level 8 FIRE monster such as Crimson Blader, you can use Spiritual Fire Art - Kurenai to tribute your monster after it has been given 2 attacks. This combo can work as an OTK with Crimson Blader if its 2 attacks were direct attacks, and by the effect of Spiritual Fire Art - Kurenai, you can tribute it for a final 2800 damage, adding on to the previous 2 attacks, totaling at 8400 damage.