"What is Last Boss, my sister?" 　　Involving Marisa and Alice, there is something suspicious from the Scarlet Devil Mansion. 　　　 One day, Marisa arrived with a letter of challenge. 　　　 "What is this?" 　　　 "I surely gave you! Bye~!" 　　　 "Well, wait a minute ..." 　　　 Will Reimu reach the mastermind, kicking out the residents of Scarlet Devil Mansion (and others)?