In 1911, Hajime was given an apprenticeship in the drawing department of the Printing Company. Soon afterwards he was introduced to Kaburagi Kiyokata, the renowned painter, and became Kiyokata's student. It was Kiyokata that gave Hajime his artist's name, Shinsui. The character shin was an alternate reading of the character fuka from Fukagawa, the district in Tokyo where Hajime was born. The character sui was derived from the kiyo character in Kiyokata's own name.
During this time, Shinsui's studies were extremely difficult since he worked during the day and also attended night school. He was immersed in art and, despite the lack of sleep, was quite passionate about his studies. It was not long before his paintings were included in public exhibitions. In 1912 his painting was first shown by the Tatsumi gakai ('Southeast Painting Society') and later works were displayed by the Kyodokai ('Homeland Society'), the Nihon bijutsuin ('Japan art institute'), and in the government sponsored Bunten show.
When Shinsui was eighteen years old, his paintings were seen by the publisher Watanabe Shozaburo at an exhibition at Kiyokata's art school. Watanabe was especially interested in creating a woodblock print from Shinsui's painting Taikyo ('Before the mirror'). He obtained an introduction with Shinsui's teacher Kiyokata and asked for his permission to attempt this experimental print. Permission was granted.
Shinsui's first print, 'Before the Mirror', depicts a young woman wearing a deep red kimono under-robe looking off into an unseen mirror. Instead of using the harsh aniline red so common in Meiji-era prints, Watanabe decided to use a natural vegetable dye to print the red garment. It was necessary to print the robe several times to achieve a rich crimson color. Special care was also taken printing the background, a speckled gray texture that contrasted with the deep expanses of red garment, black hair, and ivory skin. The final effect was simple and spectacular. Watanabe was completely satisfied and began selling the print, even though it was marked as experimental.
Shinsui continued to work with Watanabe from 1916 to 1960, designing both bijin-ga and landscape prints. He also worked with the publishers Isetatsu, the Yomiuri Newspaper Company, and Katsumura. In the later years of his life, he concentrated on painting. He was awarded the Order of the Rising Sun in 1970.