The subs will tell this better, but what's happening is the church Founder is issuing a punishment game to Rietta for doing lewd sexual activities outside the church without his permission while he was busy. The punishment game involves a confession, cuckold and gangrape show in front of the person she considered her boyfriend, so Kurt of course. Since it is a "teaching" of the church and Rietta wants to keep pleasing the founder, who has made her pregnant, she agrees and follows his instructions by asking Kurt out for a date. The founder also reassures her that after the punishment game is over, they'll wipe Kurt's memories so that they don't make things complicated for Rietta. She asks Kurt out, and he insists she drop the strange formalities with him that she'd started doing after joining the church, so she calls him "Kurt" instead of "Kurt-san" while on the date. During the date she slips a drug into his drink which makes him more susceptible to the founder's hypnosis magic, which he is normally resistant too.
At the end of their date, they both go to the hotspring under the lords castle where the punishment game begins, with Rietta apologizing to "Kurt-san" but reassuring him he won't remember any of this afterward. Rietta goes into the male bath side with the founder and members of the church, they meet up with Kurt there who's shocked at what's happening and asks Rietta who these people are, but he is immediately immobilized and then mostly silenced by the founders hypnosis magic, and forced to watch and not look away. Rietta is ordered to confess her lewd crimes and recent activities in front of Kurt, everything she's done in the church and what she did with Kateve. She's then questioned by the members of the church about what she thinks of Kurt and his tiny penis, to which she says that he just can't compare to anyone in the church, and then she's asked what the writing on her body and clothes means. She says she's a lewd dumb girl who doesn't know, apparently they mean Meat Toilet or something, and the founder says since she answered wrong the next part of the punishment game will begin. She must perform a teasing show for everyone, with Kurt now being commanded to watch carefully and not look away, as well as honestly answer the founders questions while this is happening.
They decide the punishment game will end and Kurt wins if he can resist getting an erection for the duration of the teasing show, and if he does get erect he loses, and they'll go to the next part where Kurt will have to watch the church members gangbang Rietta. The founder asks Kurt if he currently has an erection, as no one is actually sure just by looking at him because his penis is so small. Kurt says he does already have an erection, but when asked by the founder what she thinks Rietta says she's pretty sure she's seen him bigger, but not by much. They decide then if he becomes fully erect he loses. As Rietta does her tease show, Kurt becomes fully erect, but again, no one except Rietta can tell the difference because his penis is so small. However Rietta notices that Kurt has masochistic cuck tendencies and is getting off on her insulting him and his penis. She realizes Kurt is about to cum from this show so she starts insulting him and his tiny masochistic penis more directly until he finally cums just from watching her teasing show. Rietta thinks to herself that she's glad she made him feel good and that he enjoyed that, but now since he lost the punishment game it's time for her to service the church members. And that's where the first part ends!