Story
It's the near future―― Tokyo, Japan in the year 2040.
Reito, a young man with an incurable disease, makes an oath to his childhood friend Erisa that they'll meet again and enters a 'cold sleep' to heal his illness.
5 years later, he wakes up to find that the world has undergone a major transformation.

The MK (Male Killer) virus has killed 99.9% of the males on Earth. The world has become a super harem, with 5 billion women for every 5 men.

　There are only 5 male 'Numbers' who are resistant to the MK virus. As 1 of them, Reito is asked to 'mate' with the remaining women to ensure the continuation of humanity.

　A harem life awaits him in this post-pandemic world. At the same time, Reito gets caught up in a global conspiracy involving the Numbers.

Will he be able to overcome the overwhelming temptation, and save the world.