It’s been a year since Yumiko started cheating on her husband, frustrated that he’s not having sex with her. When she just started, the guy she’s cheating with forced her to read out the dialog from her husband’s Raikou doujn while they’re having sex.
Now, he’s ready to take it to the next level: he brings her to Comiket (which her husband is attending) and makes her wear a very lewd Raikou cosplay, "enhanced" with a vibrator...