Search the Fortuna Castle
Now you can activate and use Gyro Blades. You can activate it using Buster and move it with you sword. Try to move Gyro Blades into the group of enemies. Go back to the Grand Hall destroying Scarecrows on your way.
Grand Hall/Large Hall
Activate the Gyro Blades and move it to the sacrophagus in the middle of the floor. Leave this room through door to the east and go to the Dining Room again.
Dining Room/Large Hall
Destroy all Bianco Angelos here (jump over them, use f.e. High Roller or any other combo). Now go to the place where the fireballs fly along the corridor. Activate the Gyro Blade and move it into the corridor to block fireballs. Repeat it until Blades destroy the cannon. There is a Secret Mission 02 behind it. Enter the door and you will find yourself in the Large Hall again - but this time, behind bars. Destroy Scarecrows, activate blue panels with Gyro Blades and leave this room taking Gyro Blades with you. Push it along the corridor to the other side of it. You should have two Gyro Blades now, so take them to the glowing points in the center of the corridor.
Secret Mission 02: Alley-oop
Destroy demons 5 times using Buster, without falling down.
Jump and use Snatch, and then Buster. Every successful attack will launch you higher. Do it five times.
This boss has two forms. The first are Rusalkas. You can beat them without a problem - use Snatch when you find one of them flying. Then use Buster on her. The second form is much more dangerous. Try to jump and roll to avoid his attacks.