Step 1:Steal the Mage Masher from the Masked Man in Prima Vista. Step 2:In Evil Forest, equip the Mage Masher and you'll learn Detect. Step 3:When you go into Trance Mode, go to Dyne Skills and you'll see Tidal Flame.
The way to beat Asura is to let kain use jump,cecil use attack,rydia use ifrit, rosa use wall on Asura to make her white magic reflect on to you and edge use flame thats how I beat asura and more good news when you beat asura she becomes your summon
ps: she's usefull for when only rydia is alive she brings your dead people to life good luck