The topic of having an open marriage had been brought up to Mikoto by Fugaku every now and then until one day she got tired of hearing it and caved in to her husband's request. She knows he's always found Kushina attractive and have been meaning to fuck her one day so Mikoto arranged a private meet up with her best friend. Unsurprisingly Kushina mentioned how Fukagu had been acting strange around her lately and offered to help her friend in any way she could.
This is when Kushina introduced Mikoto to Killer Bee, who at this point has the reputation of fixing failed marriages, who also fixed Kushina and Minato's. Mikoto was suspicious at first but Kushina made sure she would never let Fugaku get too close to her and that this is the right time to let him know what he's been missing out by sexually depriving his wife.
Tonight was the night and Mikoto had invited Killer Bee to their home. She wasted no time and had Bee fuck her in the ass just as she hears her husband entering the room. Mikoto was enjoying every single minute of it and all Fugaku could do was watch as his wife is getting fucked in the ass by an unknown man in their bedroom. Mikoto wanted her husband to remember every moment of it so as a finale she let Bee shoot his load into her ass while he watched. Little did she know however that Fugaku didn't come into the room alone!