Chichi no Jikan follows Shinogi Kyūichi, a male biology student who lives in an apartment near a helpful female neighbor/friend, Takarai Ayaka. One day, he is visited by aliens, who demand that he raise their baby for a year... or else the world is history. The baby is apparently human, and is raised the way humans are: through breast-feeding. Kyūichi's sex is not a problem for the aliens: they give him a simple device that switches his body to a woman's with the mere touch of a button. Conveniently, Kyūichi's female form is very well-endowed.