In a World Where Males Are Nearly Extinct, Semen Has Become a Precious Resource.

A world where the birth rate of human males has dropped to 1 in 5,000. In this society, any woman who wishes to become pregnant must obtain a government-issued Fertility Band (Proof of Fertility) and wear it at all times. This signals to the few remaining males that she is actively seeking to conceive. In essence, any woman wearing a Fertility Band is ready to engage in "reproductive activities" at any time.

Pt.1: It was a day like any other, just a normal commute to school... The train our protagonist, Sato, rides has become a hotspot for women eager to secure valuable semen. Every day, he gets to choose from his own harem based on his mood—ready to reproduce!! A law was enacted to protect the survival of the human race: ejaculation must occur inside a vagina. Not once has Sato failed to follow this law...

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