Kumagusu had the honor of presenting a lecture to Emperor Showa in 1929. Thereafter, he spent many days researching and organizing his massive collection of materials with the help of his wife and daughter in preparation for establishing the Minakata Institute of Botanical Research. However, both his body and mind began to weaken by age, and soon his sickness worsened. On December 29, 1941, the great scholar of global activity passed away at the age of 74.