Gagaga Samurai

2 Level 4 monsters Once per turn: You can detach 1 Xyz Material from this card, then target 1 "Gagaga" monster you control; it can make a second attack during each Battle Phase this turn. When another monster you control is targeted for an attack while this card is in Attack Position: You can change this card to Defense Position, and if you do, change the attack target to this card and perform damage calculation.