Writing Chelsey's arc has been a struggle because it involves a matter which on the surface seems the simple but is actually quite the complex question: "why share?"
Unlike the previous iteration of WMIY where I just kind of hand waved it away, this time I spent a lot of time researching the cuckolding fetish in both men and women. For starters, I one of the first things I learned is that NTR paints a
very inaccurate picture of motivations and behavior of all of the participants. The second is that it deals with some of the beastly parts of the human sexual psyche that most people don't like to acknowledge much less talk about. That is the concept of dominance and submission. Keep in mind, this may not be to everyone's tastes because we're about to delve into the darker more primal aspects of human nature that play a large part in the motivation of a cuckquean and a cuckcake but may not be part of a normal monogamous relationship.
In truth, cuckqueans want to see their partner go from a mating partner to an alpha male of a pack. Seeing him mating with multiple partners increases his appeal in her eyes, good enough for her is one thing, but "just how desirable
is my husband" is the question the cuckquean asks herself. Being desired by multiple females gives her a sense of "look how sexy he is, every girl wants him." Seeing him as head of a group of females who are all dominant to her yet submissive to her husband makes him look more appealing.
While you will make zero friends among feminist, to a man a dominant male is competition, to a female it gives her security, as he is capable of providing for her and offering a sense of comfort and security. That is why women go for the confident guys.
Chelsey signs on for the same reason, I'm sure we've all met the girl who always seems to have a boyfriend but never seems to be very intimate relationship with them, or spend a lot of time with him? Well, if you haven't, find a girl and ask her if she knows a girl like this, one that can't seems like they simply can't function without a boyfriend, yet never stays loyal for very long. Chances are they know one. A man in her life offers a rock and confidence boost even if he isn't a big part of her day-to-day life. Chelsey is one of those, she will gladly offer sex in exchange for security, though she only seemed to hook up with men who wanted her for sex but didn't want to be there for her emotionally. So, she turned to Mary who didn't quite fit that function and often did more harm than good. Logan can serve as that during her school life, as a cuckcake(female bull) Chelsey has dominance over Molly and Logan is up-front with what he wants. He is willing to be her rock and provide her security in exchange for sex without her being exclusive, he can be a temporary boyfriend so that she can have the confidence to finally tell people "no" and assert herself yet not be tied down and take her time finding a better guy to fill that void.
The thing to keep in mind is that the girls are not replacing Molly nor are they all booty calls this time around. It is a harem but not the pretty ones you normally see in porn where all the girls get along out of a mutual love for the main character. The cuckcakes are coming into Molly and Logan's relationship for their own reasons and are willing to trade sex, but there is no exclusive agreement. Whether the cuckcakes remain exclusive to Logan or not is their decision, but ever noticed it's a lot easier to cheat on a girlfriend than it is to get a girlfriend? Women are drawn to men who are proven reliable by having other females, so none of the cuckcakes are technically tied down, they have no desire to seek out another male. Molly is exclusive to Logan, though she will offer sexual favors to the cuckcakes as a show of submission. Logan can only sleep with partners Molly approves of.
A normal two person relationship is a complex web of needs, wants, and compromises, once you add the third, fourth, or fifth person, things become even more crazy.
It should also be noted that "sharing" is not the ideal relationship for the cuckcakes, while there will be side girls that simply want to have a fun romp, for the girls that are going to actually join the relationship, it will be more akin to desperation than romance. Though the circumstances will be different, for some like Chelsey, they simply need some support, though for others it may be a kink or a desire.