Otokojuku Side Story: Crimson!! Women's Private School

Otokojuku Side Story: Crimson!! Women's Private School manga summary: The year is 20xx, and Japanese men are a dying breed. At the end of World War III, Japan was hit by a Man-Bomb, which rewrote the DNA of Japanese men, weakening them and stripping them of their will to fight. Those that survived gave their lives to save their country. But the Spirit of Yamato still lives on... in the Japanese women!