While Moroi had been active in the Tokyo musical scene, forming with other colleagues a society named Surya, he claimed that his creative life truly started from his Berlin days.
Returning to Japan in 1934, he built a successful career in subsequent years.
His work was part of the music event in the art competition at the 1936 Summer Olympics.
Following the country's surrender he focused on teaching and writing books on music theory, composing just eight works in the following three decades, including two more symphonies.
Pupils of Moroi include Ikuma Dan, Toriro Miki, Toshiharu Ichikawa (市川都志春), Yoshirō Irino, Kunio Toda (戸田邦雄), Minao Shibata, Sōkichi Ozaki (尾崎宗吉), Akio Yashiro, Chūji Kinoshita (木下忠司), and Im Won-sik.