Select 1 Level 4 or lower "Superheavy Samurai" monster in face-up Defense Position that you control. It becomes a Tuner Monster. If you do not Synchro Summon a monster during the turn you use this Skill, all monsters in Defense Position you control will be sent to your Graveyard. This Skill can only be used if you begin the Duel with a Deck that does not contain Spell/Trap Cards. This Skill can be used only once per Duel.