Shuumatsu no Harem

is a Japanese manga written by LINK and illustrated by Kotaro Shouno. Seven Seas has licensed it for English release. A spin-off titled started serialization in Shounen Jump Plus in April 2018.

Plot
In the year 2040, new energy sources and advanced technology have boomed the possibilities for all of society's infrastructure and left handled by AI and machines with minimal input from humans. Pharmaceutics student, Reito Mizuhara confesses his feelings to his childhood friend and fellow student Erisa Tachibana. Their newfound happiness is short-lived however, after Reito has been diagnosed with Multiple Sclerosis which is considered incurable at present. To save his life, Reito must enter a 5-year cryogenic suspension until a cure is found and is forced to temporarily separate from his family and lover.

After 5 years, Reito awakens to find his world turned upside-down after a genocidal virus takes down 99.9% of Earth's male population. Now it's up to Reito to either save the world or repopulate the Earth by mating all of Earth's females.