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… Our protagonist has started groping and sucking their tits while feigning it to be just a massage… Eventually the other girls get involved….