This study aimed to analyze Shonenkurabu (少年俱樂部, Boys' Club) as a medium that presents notions about modern war to children. This magazine has been instrumental in creating the concept that “Warring humans are synonymous with justice.” However, there has been no controversy raised concerning the main role that Shonenkurabu has played in this matter. In addition, the awareness about war that the readers have attained through communication with the magazine has not been discussed. This study identified the process whereby the magazine Shonenkurabu introduced boys to images and ideas about war from the aspect of a mass media strategy and readers’ involvement in such a strategy, and examined children's war literature that is at the center of the process. Especially, Yamanaka Minetaro’s 300 Miles behind Enemy Lines (敵中橫斷三百里) was researched, which could be regarded as the original form of such war literature, and its contextual background was examined. Through this, an understanding about how contemporary Japanese youth gain awareness about modern war was presented.