Tsubasa Shiina  

Ten-year-old Tsubasa Shiina lost her mother at birth, which led to feelings of guilt throughout her life. She is shy and unsociable due to this loss. One night, while out fetching her ranch dog Tenmaru, she witnesses a UFO crash in the forest near her home. As she approaches the wreckage, she sees the remains of the downed spacecraft, its semi-conscious pilot, and an alien organism called "Maguar". Fearing for her life, Tsubasa runs into the spacecraft to escape. However, she is cornered by the Maguar and nearly killed. Just as all hope seems lost, a mysterious organism known as "Ribers" fuses with Tsubasa to become Figure 17 and defeat the Maguar. To her surprise, Ribers separates from her and takes on the form of an identical copy of herself named Hikaru, making Tsubasa's new twin sister.