Hiwatari's parents owned a bookstore while she was growing up, which gave her easy access to reading books, magazines and manga.
She especially liked the science fiction novels of Shinichi Hoshi and Yasutaka Tsutsui as well as manga by Osamu Tezuka, Hideko Mizuno, Yumiko Oshima, Moto Hagio, Keiko Takemiya as well as Ritusko Abe's Suekko Taifū, Mitsuteru Yokoyama's Babel II and Masami Kurumada's Saint Seiya.
[1] Her first work, Mahōtsukai wa Shitteiru (I Know a Magician) was published in the weekly anthology Hana to Yume (Flowers and Dreams) in 1982.
[2] Her best-known work was Please Save My Earth, a 21-volume series concerning several alien scientists who are reincarnated as high school students in modern Tokyo.
After finishing Please Save My Earth, she was troubled about not creating another series as successful as her previous one.