Due to the way the game handles stacks of arrows, it's possible for a character to fire their last arrow without losing it.

When a character fires an arrow, their arrow count is decremented by one. If the count would be reduced to zero, then instead, the count stays at one and the game sets a flag indicating that the stack of arrows will be removed when the character next comes up in the menu queue (i.e., when their menu is about to pop up). See: ATB System for more details.

Since the last arrow check only occurs when a character comes up in the menu queue, there are ways to exploit this to retain the single final arrow.

If a character never re-enters the menu queue due to the battle ending, they will not lose their final arrow. Therefore, if the character gets the killing blow, or if the battle otherwise ends before they come up in the menu queue again, they will retain the arrow.

If the battle will end without any further inputs from the player¹⁾, then waiting at another character's menu until the battle ends will prevent the last arrow from being lost.

If a character becomes berserked before re-entering the menu queue, they will effectively have infinite arrows. The easiest way to ensure this happens is to have the character berserk themselves, via the Bersk spell or the Bacchus j-item.

It is possible to get the same effect when Bersk is cast by a different character, but the target (the arrow user) must not re-enter the menu queue before Bersk takes effect. It can be difficult to tell when this will happen, but in general, the sooner Bersk is cast after their last action, the less likely they are to have entered the menu queue again.

The simplest way to guarantee this will work is for the target's menu to be open when Bersk takes effect.

It is also possible to avoid losing any arrows at all (even at stack sizes greater than one) if the target's arrows are moved into the inventory when Bersk takes effect (assuming no command has been entered after doing so- this is effectively the same as the Avenger/weapon-swap glitch). They will attack using the punch animation, but continue using the stats of the bow and arrows they had equipped.

If the berserked character loses berserk via death, Black Hole, Stone, etc. after firing their last arrow, they will lose the arrow the next time they come up in the menu queue (if they do so before the battle ends; leaving them Swooned or Stoned will save the arrow).