Kase,Kamen Rider Siren's ventaran form.
Kase holds out the siren deck and says "Kamen Rider!" transforming into Kamen Rider Siren.
Kase as Kamen Rider Siren.
Kase is a fellow survivor of Ventara, like Captian Harlock, and has the ability to transform into Kamen Rider Siren, the sole female Kamen Rider, with a swan Advent Deck. She is an eager hunter who acts the complete opposite of Captian Harlock, who was unaware that she had survived.
Her Theme Is All I Ask of You (Kase's Theme)
Kamen Rider Siren's rapier sword, the Blanc Visor, where she can place her cards into the crossguard slot.
Kamen Rider Siren's Guard Vent. Siren summons a white bird themed shield that she can use with her rapier sword for a combination of offense and defense.
Blancwing, Siren's advent beast. It is a mechanical swan capable of blowing powerful gusts of wind.
Kamen Rider Siren casts an illusion spell that makes her disappear replacing her with dancing whirlwinds of feathers in her place around the enemy, distracting them and leaving them open to attacks.
Kamen Rider Sirens Sword Vent. Summons her double bladed Naginata sword named Wing Slasher.
Kamen Rider Siren's Final Vent Part 1. Blancwing shows up and flaps its wings blowing powerful gusts of wind that blows groups of enemies from the ground into the air from its attack towards Siren.
Kamen Rider Siren's Final Vent Part 2. Siren uses her Misty Slash technique where the enemies blown away are sent towards her to be slashed along by her double-edged sword to injure them or slicing them apart creating kinetic explosions from the force of the final vent.
