She was breast-fed by her mother and was growing well, and on March 3, 1928, and it was planned for her to attend her first festival on a grand scale. Her parents prepared 30 kinds of hina sweets, and gifts were prepared from the Kuninomiya family, the family house of Empress Kōjun, and from the princesses of Emperor Meiji who became consorts of the Imperial Palace.[6] The princesses were Princess Masako Takeda, Fusako Kitashirakawa, Princess Nobuko Asaka, and Toshiko Higashikuni, who would be considered "great aunts" of Sachiko.
On the morning of February 27, she suddenly developed a high fever.[7] The symptoms of eczema that had been present in the past worsened, swelling of the right submandibular lymph gland was also observed, and a diagnosis of pharyngeal catarrh was made.[8] The New Year's holiday celebration was postponed, and the Empress and court physicians took care of her. On March 1, when the onset of the illness was announced, doctors said that "it was not enough to worry about".
However, at 9 pm on March 4, her temperature rose again to around 39 °C, she was in critical condition, and sepsis was suspected.[9] The empress and her ladies-in-waiting stayed up all night to nurse her. At the same time, her father had a fever, but this was due to a cold. By the afternoon of the 5th, her physical condition seemed to have recovered, but after the morning of the 6th, the high fever continued again.[7] The events planned for the Empress's birthday on that day were cancelled, and her maternal grandparents, who were staying at Atami, were requested to return to Tokyo by midnight.
At 4 pm on the 7th, she was diagnosed with a complication of sepsis.[7] At 3:30 am on the following day, she became critically ill, and at 3:38 am she died in Akasaka Palace.[10] She was 5 months and 27 days old.
Later, entertainment broadcasts and Army Memorial Day events were voluntarily suspended. Article 17 of the Imperial Funeral Ordinance did not apply to Sachiko who was under the age of seven, so a simple funeral was held on March 13, and she was buried in Toshimagaoka Cemetery.[11][12] The chief mourner was Yahachi Kawai, the Empress's domestic administration.[13] On March 19, the Emperor and Empress, accompanied by Sachiko's older sister, Shigeko, visited the Toshimagaoka Cemetery and paid their respects at Sachiko's grave.[14]
Empress Kōjun said that, out of grief, she held a doll of the same weight for a while afterwards. The empress also gave a grant to Keifukukai (now the Social Welfare Corporation Imperial Gift Foundation, Keifuku Childcare Association) and the organization established the "Late Princess Sachiko Hisa-no-miya Commemorative Child Protection Fund" which created facilities throughout the country and also overseas for the protection of infants.[15]
