Ad-libs are special attacks that have a chance to randomly and automatically occur during battle after special needs are met. For example, one of Tsubasa's ad-libs has a chance of activating when using a Lance skill. Aside from Itsuki, who gains his through story progression, Ad-lib Performances are earned after completing a specific character's respective side stories.
Ad-libs, while dealing damage, usually have special effects as well, such as inflicting status ailments like Confusion and Charm to enemies.
Ad-libs always succeed at damaging enemies, even if the enemy is normally immune to the attack's element.
Of all playable characters, Mamori Minamoto is the only one that doesn't get an Ad-lib Performance from her Side Stories, as she solely gets Special Performances from her Side Stories.