Sana, the daughter of the Chiba Dojo (martial art gym) in Okemachi Japan, had promised to marry Ryoma Sakamoto, a TOSA Samurai who was assassinated by an unknown killer at the end of the EDO period. He was once the dojo's headmaster and Sana’s brother's best friend. While Sana was in charge of the Dojo when the master was absent, a woman called Ryo, who claimed to be Ryoma's wife before he was killed, appeared before her …. and eventually, Sana became involved in a mystery surrounding Ryoma’s assassination.