1.So most male non-virgin turned into monster. At chapter 1 mc friend show some sympthon of it. The government or whatever it is decided to kidnap virgin and make them as test subject. The girls are forced by the government to take the man virginity if they failed they will sent to physical labour camp and face fate worse than death. By governent , it was ruled by woman, kinda like world end harem manga, they are sexist and will kill man without hesitation and choose the one who sucess at experiment.
2. They decided to make vaccine and tested it on the virgin, mc seems not virgin, at jail break arc, mc got knocked out and they do some weird shit on him, it implied he was raped. AS why the girls must seduce them, i think they can't force the guy and need to fulfill some condition that the virgin must have sex with consent or something, just shut your brain off when reading this manga. btw they decided to kill the man who lose their virginity on the test subject because they have the possibility to become monster after sex. Edit : they can actually force the guy, tie them up and rape them, the reason they play silly seducing silly sex game is because the childhood friend is the head warden , and because she was kind and want mc live, she decided to somehow try to prolong mc life , hoping he survive till the end to the point they managed to find the vaccine, mc and his friends was just one of the project, there are many men who suffer the same fate as mc, and they was forcefully raped and killed as vaccine testing drug. MC seems raped in first arc and they give him some vaccine, i think it implied mc was immune to virus...but sadly if mc bear a child, if the child was male, thechild will mutate into monster if they lose their virginity. They are searching for a man who can bear a male children who are immune to the virus.
3. At chapter 104 which the ending, one of mc friend turned to monster but he still remember his memory as human and can control himself. He even helped mc and such. The guy who kissed mc childhood friend is the one who immune to virus and the sucessful test subject, he can have sex without turning into monster(including his baby). The guy and the other 2 girl tells the turned monster man to go with them(if not they will kill mc and the other girls) and saying they also need him as sample for the virus because he also the only one who managed to have human sanity after turned to monster. The childhood friend got kissed by the guy and left crying with the guy, 2 other girl and the man turned monster. It implied she do it to save mc , they then left with helicopter. MC was left on the island with his other 2 male friend, and 5 other girls and vow to save his childhood friend.
4. the childhood friend got punished because she failed the first experiment and the higher up found out she try to save her childhood friend, they then give her some sort of experiment, turning her body to super human. She have monstrous strengh, she easily punch a stone pillar and make a hole on it, the effect on the experiment was she have memory loss, that's why she acted cold towards mc at the raws you guys reading
5. for the sequel, It seems it was sequel with same plot haha this was web comic btw, after chapter 104, they continue it to the sequel.
