Kiriko Endo is Kenji's older sister. She was interested in studying about pathogens and microorganisms since she was young. Her beloved one used to be Moroboshi, but the first Friend told The Assasin to kill him so that he could be Kiriko's husband and make her "The Holy Mother" just like what his The New Prophecy Book said. Kiriko married Friend and gave birth to Kanna, but when she realized about Friend's creed. In 1997, she left Kanna with Kenji and their mom Jiyo and then disappeared. Kiriko is the one who invented both the Virus Friend used as his weapon of humanity annihilation and its cure, the Vaccine when Friend required it to act as the hero of humanity instead. In 2014 A.D., Kiriko opened a Vaccine Facility in America, but then it had been incinerated by Friend's henchmen. Fortunately, Keroyon came and saved her life. Kiriko lived in Keroyon's Frog legion fortress and invented a new vaccine for Friend's final virus when Maruo came to the fortress. After Friend's annihilation plan was unsuccessful , Kiriko went to Africa to aid sick African people, and then Kanna and Chono, who also brought an elder Jiyo, came to see her.