Hoshino was born on April 21, 1980, in Shiga Prefecture, Japan, as the younger of fraternal twin girls and the second of three children.[1] As a child, she originally dreamed of becoming an astronaut.[2] She drew her first manga at twenty-one.[3] In 1998, Hoshino moved to Tokyo. She dreamed of bringing her mother to the city and was able to in 2006.[4]