A friendly, ordinary sibling and sibling takes on a challenge! They are the first time they've ever taken an aphrodisiac in a locked room, alone in the room where they are alone! When a shy virgin brother and a kind sister try to take on a naughty mission, will the two, whose crotches are slimy with excitement and end up in forbidden incest?

A serious, genuine, close sibling and sibling attempts a monitoring experiment to get a prize! Under the title "What is the boundary between siblings and men and women?", the group thoroughly examines the extent to which skinship can be achieved by siblings (after secretly giving them an aphrodisiac). The two of them complete the mission despite being embarrassed, but the fires start to cause many siblings to have sex and incest! They are so tempted that they lose their virginity as they are too excited!