As a child, he would often spend time in a grove of Tsuki-jō [ja] in Saitama, consisting of trees that were several hundreds of years old.
He focused on a series consisting of short stories in order to still experiment with styles and themes in the beginning of his career.
He made a name for himself with the series Little Forest, which he published in Afternoon from 2002 until 2005 and which was based on his own experiences of living an autark life.
[5] Igarashi lived for three years in the countryside of Iwate Prefecture, where he was working in rice fields, and his editors approached him about making a manga series about his life.
In 2005, French comic artist Frédéric Boilet invited him to create a short story about Iwate Prefecture and the cover illustration for the French-Japanese anthology Japan: As Viewed by 17 Creators.
[1] He is known for drawing plants and animals with a lot of realism as well as for his "maximalist" spreads showing panoramic landscape views.
[7] Most of Igarashi's human characters are often drawn in a simple and sketched way in order to differentiate them from detailed backgrounds and accounts of nature.
He reasons that femininity is connected with nature and that drawing cute female characters gives his work a bigger mass appeal.
[2] In Witches, he draws on mythology and fairy tales around femininity to show different women being ostracized or excluded from society by patriarchy.
[2] He names Hinako Sugiura as his favorite manga artist and he used to read Akira Toriyama and Rumiko Takahashi.
[1] His work has received praise from other manga artists like Taiyō Matsumoto,[10] Hiroaki Samura[4] and Naoki Urasawa.
[13] Several of his manga have been translated into other languages, among them English,[14] Korean,[15] French,[16] Italian,[17] Spanish,[18] Czech[19] Polish[20] and Serbian.