Hisashi Inoue, honorary professor at Surugadai University, said the March 24 incident — in which a Japan Self-Defense Forces (SDF) officer broke into the Chinese Embassy in Japan carrying a knife — was extremely serious and shocking, and constituted a grave violation of the Vienna Convention on Diplomatic Relations. Inoue, who is also chairman of the Japan-China Friendship Association, noted that the Japanese government has yet to issue an apology to China and that merely expressing "regret" is inadequate. He called on the prime minister and defense minister to formally apologize to the Chinese side.