From Onee Chanbara, the Lone Sister Swordswoman Aya

Special characters and the weapons owned by those characters can be obtained.

Aya, the lone female swordswoman from the zombie-infested world of Onee Chanbara, has entered the battle. She is wearing her trademark ten-gallon hat and bikini, and of course, she carries a Japanese sword.
Aya is a master swordswoman who usually fights off zombies, but it looks like she's going to give her all to help the Earth in its time of need. Her SP attack, the Ecstasy Combination, is quite powerful. When it works, it WORKS!