Unlike Damage Up, Defense Up can lower thresholds on certain enemy weapons. For example, the .52 Gal does 52 base damage, which is a two-shot splat on normal Inklings. Defense Up can drop the weapon's damage to below 50, making it a three-shot splat with the .52 Gal. This allows players to take extra hits from certain weapons. However, if an opponent has Damage Up, then the effect is canceled out, as the damage boost will again bring the weapons' "shots-to-splat" back up to normal.
Graph showing the effect of stacking Defense Up to defend against 2-hit+ splat weapons.
a = Ability Points of Damage Up = 10 × [Number of Damage Up Main Slots] + 3 × [Number of Damage Up Sub Slots]
d = Ability Points of Defense Up = 10 × [Number of Defense Up Main Slots] + 3 × [Number of Defense Up Sub Slots]
A = (0.99 × a - (0.09 × a) ^ 2) / 100
D = (0.99 × d - (0.09 × d) ^ 2) / 100
When Damage Up ≥ Defense Up
Damage = [base damage] × [1 + (A - D)]
When Damage Up < Defense Up
Damage = [base damage] × [1 + (A - D) / 1.8]
An Inkling wearing an outfit with all Defense Up mains.