Yuna’s Overdrive is not technically an ability to be used in battle like other Overdrives. Using Grand Summon is similar to using Yuna’s regular Summon command however the Aeon will enter the battle with a full Overdrive meter allowing that Aeon to use an Overdrive immediately. If the Aeon already had a fully charged Overdrive meter it will be able to user two Overdrives back to back.
For more information on the Overdrives for individual Aeons refer to the Aeon subsection.
