Contains a side story called Haha ga Kita Hi (Mother's Day):

Mizuki seems like a normal boy in highschool. One day he gets a strange visitor who gives him a cake that seems delicious, yet his friends can't seem to stand it. Then, an oddly familiar woman appears who acts very shocked to discover that he's a boy, going so far as to rip off his shirt just to know his gender. Then things really get weird for Mizuki.