When attacking with Yasuo Remorseful, if the opponent moves a unit away from the battlefield in response but another unit remains there, can you target the remaining unit, or was the target locked in when the ability went on the chain?

Ruling: You must choose the target when Yasuo's attack trigger goes on the chain. If the opponent moves that targeted unit in response, the ability resolves with no effect and you cannot choose a different target.

Sequence:

• Move Yasuo to a battlefield
• His attack trigger goes on the chain and you choose your target at this time
• Pass priority; opponent can cast reaction spells
• If opponent moves the targeted unit, it resolves
• Yasuo's ability resolves with no effect since the original target is no longer at that battlefield