The post-war Showa 30s, where nothing was satisfied. The entire country of Japan was in a frenzy over events symbolizing high growth, such as the Tokyo Olympics and the opening of the Shinkansen. Women born in such an era, now in their 50s and 60s, are fully mature ladies. They grew up with a sense of lack, so even in today's era of abundance, they feel a lack of something and are a generation that desires something every day. But they can't do that because of their age. So when they get a chance to have a penis, they happily devour it in 40 wild sex sessions.