After a brief stay in Nagasaki, and a thwarted affair with a distant relative of his father, he entered the Buddhist priesthood and was given the name Harue ("spring bough," usually a feminine name). Shortly after, he fell in love with Oka Yoshie, a local poet. His family opposed the marriage until he agreed to succeed his father as the local priest. Shortly after, his father died and he began auditing classes in theology at what is now Taishō University while continuing to paint in his spare time. In 1917, he was hospitalized for pleurisy. On his way home to recuperate, he became ill with the flu, which turned into pneumonia. Although in critical condition, he recovered but had missed so much time at the University, he decided to quit school and concentrate on painting, after which his family withdrew financial support. Koga’s interest in the arts was not limited to painting. He was also an avid fan of poetry, and for a time considered a career in naniwabushi, a traditional Japanese style of musical theater. Koga also developed a deep appreciation for Asakusa Opera, an extremely popular form of light opera staged in the Asakusa district of Tokyo, and would frequent shows in the late 1910s and early 1920s. Koga’s love of Asakusa Opera was generally disapproved of by his colleagues in the Japanese Watercolor Society, as it was as considered a low-class art. Avant-garde artist Koga’s formal debut as an artist occurred in 1922 when two of his paintings were chosen for the Nika Exhibition, an exhibition dedicated to showcasing younger Japanese artists and artists utilizing experimental and modern styles in their works. Of these two paintings, especially notable is Burial, a "Cubistic" painting which art historian Chinghsin Wu argues was partially inspired by Spanish classical painter El Greco's painting The Burial of the Count of Orgaz (1586) and was painted in response to the stillbirth of Koga's daughter the year before. Thereafter, Koga continued to have his paintings accepted into the Nika Exhibition every year until his death. In 1926 he became an associate member of Nika and later a full member in 1929. In 1922 Koga assisted in the formation of the avant-garde art group "Action", which endeavored to create art candidly and without the potential limitations of existing artistic movements. Koga’s involvement in Action also gave him access to Western art works and publications, as