Ranka is the daughter to researcher Ranshe Mei, the leading scientist aboard the 117th Long Distance Research Fleet, who worked alongside Dr. Mao Nome. She is also younger sister to Brera Mei, later revealed to be the cyborg Brera Sterne. When Ranka was conceived, Ranshe was infected with the "V-Type" infection that was slowly killing her, but Ranka was born immune to it. This allowed Ranka to have a deep physical connection to the Vajra via her songs, that seemingly mimics the actions to that of a Vajra queen. It's because of this the Vajra were lured to her singing and caused the attack on the 117th Long Distance Research Fleet. Ranka doing her famous pose while singing Seikan Hikou (scene from episode 12).