The protagonist spends his boring days just going to and from school. There are three busty beauties in his class, they are far removed from him as he is an introvert. Although nothing is exciting about his life, he enjoys a reasonable daily life with his two otaku friends. But he also has a secret. One of the busty beauties in his class, Mizukawa Hiyori, is actually his childhood friend and lives in the same apartment building. Moreover, they have been studying for tests together since long ago. Today was supposed to be just like one of those days, where Hiyori comes over for a study session with our protagonist. But little did he know, Hiyori had... other plans... she threw herself onto his body, expressing her pent-up feelings... and so his road to success begins.