Muchi Muchi Kyosei Seicho Ata

Our protagonist is a teacher of a small class of girls. One day he gave the girls a snack, but that snack ended up having some HUGE effects! They grew up! They behave just as they did before, despite their voluptuous bodies... Receiving lots of their unintentional temptations, his patience is about to run out... (Source: hanime)