you should cancel it then

You should delete the giveaway and create the one for Coromon. Unless you actually have 2 keys for this game, then you can edit the key before selecting send.

Delete this

Make a deletion request ticket (unless this is the case drbeckett is describing).

Please note the following:

1. Once a giveaway ends, you'll still be able to adjust any keys before sending them, giving you the chance to swap any mispasted keys if needed.
2. Once a giveaway ends, only the listed giveaway [in this case, that'd be Symphony of War] will count for a "Received". Any other content provided by the GA creator [such as Coromon], accidental or intentional, will be considered a bonus gift for the winner, and will not affect the need to send the actual listed game.
3. Giveaways CAN be deleted if both parties agree, but it's generally a better idea to use the automatic deletion function in the bottom left of a giveaway listing's page (you can also access this through the support page by putting in a deletion ticket there; It's automatic either way.) Doing so avoids the need to get winner approval for the deletion, and also refunds any invested P to active entrants, thereby being a better option for all involved. This automatic deletion function becomes unavailable once the giveaway ends, but the only penalty for using it before the giveaway ends is the loss of a giveaway slot (which you'd lose to a Not Received anyway).
4. If you lose too many giveaway slots through honest mistakes (eg, any that required you to delete a giveaway yourself), you can just put in a support ticket requesting staff provide you with additional slots. These requests are almost never denied. On the other hand, if they're lost through problematic reasons (for example, not being able to reclaim a slot due to it being marked Not Received) staff is unlikely to give you more slots. In that sense, it's much better to just delete a faulty giveaway than to risk it being marked as Not Received, as the first one doesn't technically harm you in any way, by long-term considerations, while the second approach may leave your account unable to create further giveaways until you provide a key to a winner.

Thank you for the opportunity