Kono Minikuku mo Utsukushii Sekai EP4 - Life from This Point On

Ryou takes Akari home with him and soon his little sister Kimi starts to grow fond of Akari in spite of herself, and the three wind up declaring themselves a family, after which Akari moves into the Ninomiya household. Akari is introduced to Hikari and learns that she too came from space. Jennifer suggests that they used to be one being with no body, and then divided into two and gained bodies after they got to Earth.