Imperialism is a policy of foreign expansion promoted by a nation. There was a lot of debate back then about whether imperialism was necessary or unnecessary, good or bad. In 1901, Shusui Kotoku called imperialism "the monster of the 20th century," an unscientific entity that suffers itself first in order to make others suffer. Ishibashi Tanzan's famous argument was that he advocated the idea of a small Japan, arguing that expansionary policies were not in Japan's interests at all. However, Japan's expansionary policy continued to be pursued with great risks, eventually leading to a tragic war. Were scientific benefits and risks assessed in the process? Was a national governance system that could become dysfunctional left unaddressed? Was there a way to bring imperialism to a soft landing? In the Japanese History Laboratory (Professor Gonsuk Nagai), in order to prevent us from wandering down the path we once came to, we are trying to evaluate history and think about options that were not chosen but remained possibilities. I am working on it as a research topic. If we look closely, we can see that there are dangerous policies even in this day and age, for which we do not know what purpose or future vision they are promoting.