Mizuhara Reito is an ordinary boy who wakes up in a world of 5 billion women and 5 men. Now it's up to him to repopulate the human species. Can he stay loyal to his missing childhood friend when all humankind is counting on him to sleep with as many girls as possible?
Four years ago, a new type of virus, 
called the MK Virus,
Hace cuatro años,
un nuevo virus, el MK,
Hace cuatro años,
un nuevo virus, el MK,
Il y a quatre ans, un virus appelé
« virus MK » s’est propagé sur Terre.
Quattro anni fa un nuovo virus,
chiamato virus MK, si è diffuso in tutto il mondo.
Há quatro anos, um novo tipo de vírus,
denominado Vírus MK,
Четыре года назад новый патоген,
вирус УМ, распространился по всему миру.