So, I just went through the extra content. It was pretty good, the ending left a lot up to imagination.
As said before, the content is accessed by talking to Johnny in the recollection room after beating the game. The scene starts of with Johnny in a closet, peeping at his wife, Mary and the MC's wife, Chloe, both on a bed with two strangers. Johnny then flashbacks to how he got in the situation. The story takes place after the rest of the game, so after their wedding anniversary life's gone back to normal, normal for them being their regular swapping sex. Johnny's been getting more perverted however and he's looking for new ways to enjoy his ntr fetish. Johnny comes up with an idea of switching wives for an entire month, with the wife completely loyal to the given husband. I believe it is more like, in one month one of the husbands get both wives and in the other month, the other husband gets the wives, so one dude has two chicks and the other dude has none. (Could be different but that's what I got from google translate). So for the first month, Johnny's got both Mary and Chloe and so he decides to make them have sex with complete strangers in the city (not smart). Next scene, there's the two stranger dudes in the street trying to get laid but with no luck. They're both best friends and also virgins (Pretty much like the MC and Johnny before they met Chloe and kick started their events) and when their 5th attempt at getting laid for the day fails, one of them's about to give up to go jack off to some comics. In comes Chloe and Mary who seduce them both and invite them to an inn for dinner. Now at the dinner table, the two strangers and the two wives are talking, the strangers being pretty nervous and making it obvious that they're virgins and have no experience. The wives go off to the restroom to chat and the two strangers realize that they blew their money on food and don't have enough to invite them to stay the night at the inn, quarreling ensues. In the restroom, the wives are just talking about Johnny's growing kinkiness and also the strangers reminding them of their first times with their husbands (since both husbands were virgins). Girls come back from restroom and tell the two dudes they already had their own room, dudes are happy, sex scene proceeds.
So now Johnny's flashback is done and we're back in the room with Johnny in the closet peaking at his wife, Mary and kinda wife (teacher, obedient partner for one month, etc.), Chloe and the two strangers. So, Johnny's in the closet expecting some basic sex since he found out they're virgins, plus there was also a no-kiss rule for the wives. The sex scene ensues and starts off a bit awkward with some foreplay since the two dudes are virgins. Chloe starts sex first, immediately breaks no kiss rule, Johnny looks on but doesn't want to break out of the closet like some madman voyeur (plus the two strangers don't know the wives are actually married). Sex continues, dude cums, happy times. Scene moves back to Mary, turns out the other dudes foreplay, despite being a virgin, made her come one or twice. This makes Johnny feel a bit down since he only managed to make Mary cum during their fourth time having sex while this random virgin stranger made her cum twice with foreplay alone. Then again, this only serves to turn him on more. More forbidden kissing ensues, this time between Mary and one of the strangers, Johnny still doesn't stop the kinky play. After both wives have had a good amount of sex, it halts for a bit (by now its clear that these women don't really care about any rules set and Johnny's too into it to stop it.) Johnny believes everything's done til one of the girls say she feels a bit grimy and one of the dudes suggests a shower, a group shower. This of course, wasn't in Johnny's plans but the women don't really care so all four of them head on to the shower. Johnny eventually gets out of the closet once he hears moans come from the shower and he looks at the silhouettes of the wives and strangers having sex. They're doing kinky shit in the shower, girl complains cum gets in her hair, etc. Johnny continues looking at the scene, expecting it to end shortly. It doesn't. Johnny looks on, forgetting about the time, apparently it turns evening while their in the shower so apparently they've been fucking in there for and hour or two. By now the girls are pretty worn out by now and Johnny feels like he's been one-upped by virgins, though no longer virgins (which he most likely has). One dude says that they should come out of the shower, Johnny snaps back to his senses and rushes back to the closet, fully expecting everything to be over. Nope, wives and strangers start round three. A bit into round three both girls gets thirsty, quenches their thirst in their own kinky ways, Chloe sucks dick to get hydrated whereas Mary exchanges water with another dude mouth-to-mouth (both unhygienic and clearly breaking the no kiss rule again). Johnny looks on, his dick is pleased. the wives and strangers then practice every sex position known to man (hyperbole, but point is, its a lot of sex positions) and finally it seems like everyone's been satisfied. All the sex has calmed down, though both girls are pretty much jacking the dudes off. Sexy comments from the wives on how they both believe that it was the best sex they've ever had (RIP Priest, you will be missed) and also praises their cocks. Johnny is pleased but frustrated, the usual dilemma of enjoying your wives having sex with others but also being distraught about it. Women break the ice, asks both dudes if they want to try anal sex. Johnny's super confused now. He thinks back to when Sauber took both wives' anal virginities on their anniversary and that both wives have refused to have anal sex with Johnny and the MC, their husbands, but they're both ready to have anal sex with some virgin strangers they met a couple hours ago. Anal sex ensues, girls love it. After the anal sex scene, the scene cuts to just Johnny, still in the closet and Mary on the other side of the closet. Chloe is gone and so are the two strangers (graduating from their virginities in the best way possible). Mary opens up the closet and sees Johnny in a poor state, tears in his eyes, dick in hand and a good amount of jizz. Johnny's next comment contradicts his appearance when he says that it was awesome. Scene cuts to Mary and Chloe walking in the city. Mary complains about Johnny, calling him stupid. Chloe responds that they might've made his kink worse by accident, though admits that she really enjoyed the sex with the two strangers. Mary agrees and ask if she would want to do it again, Chloe responding with a blushing, but pretty seductive face, implying yes, Cue the two former virgins walking down the street, the girls see them both and presumably chase after them so they can have more sex, this time without the knowledge of both of their husbands. Scene cuts to black, with a 'The End?'. The question mark implies that we might have more extra content or at least see the characters return in another one of the circle's games cuz he likes to do that.
So yeah, the MC is nowhere to be seen in this little extra, though he is mentioned a couple of times by Johnny and as I said, a lot of this is left up to your own imagination. The girls seem pretty into the sex with the two dudes but sometimes your left thinking what they're intentions are since you're watching from Johnny's POV. The girls seem to be somewhat worried about Johnny's growing kinkiness and maybe tried to shock him by going overboard with the strangers and disobeying the rules that Johnny set out. Or they could have simply been going along with the play but get getting a bit absorbed in it while occasionally remembering Johnny's presence in the closet. The girls could have been acting to make the virgins feel like they're good at sex or the virgins were so good at sex that they they disregarded the rules and went all out, then saw them in the street and decided to cheat on their husbands. I'd like to believe they decided to cheat on their husbands in the end because the two strangers were sex machines but that's just me. Knowing this circle however, it'll likely stray away from that territory (the exception being the game with Lloyd). But yeah, that's it. 10/10 would fap again. Support the circle.