On December 22, the first session of the 5th Korea-Russia Science Day was held with the participation of the Russian Academy of Sciences, the Korean-Russian Center for Cooperation in Science and Technology (KORUSTEC), the Russian Foundation for Basic Research and the National Research Foundation of Korea with the presence of the Science Attaché of the Republic of Korea. The main topic was the international cooperation of the two countries within the Millimetron space observatory and top astrophysical problems that can be solved with it, as well as the development of ground millimeter astronomy facilities in Russia.