Akarui Sekai Keikaku aka The Smutter Games 1-6
This is like some bizarre hodgepodge of various manga. Some guy from the Japanese government, wearing a mask and acting like a troll from 4chan, goes to a Japanese school and declares to stop Japan's birth rate problems everyone in this school must become lovers or die. Within a month everyone in the school, except for 9 students, becomes lovers. These students include the main character, who is basically a more pathetic version of Keima, his insane lover who is a yandere on level with Yuno from Mirai Nikki and a loli who is basically a kinky version of Rikka from Chuu2. The troll proceeds to give the group a bunch of missions to get them closer together and if they fail then they'll die. Seriously, this thing is like the height of stupid but entertaining.