You couldn't deny that you were more than a little curious what it would be like to share your bodies with a literal sex demon. Though you were concerned about what this meant for the app going forward, you decided you could roll the dice and hopefully be able to undo the merge if things went bad. While you hoped it wouldn't be necessary, you had a feeling the app could also be used to make Mona forcibly forget it, or even ignore its existence completely. However, a bit more info was needed first.
After finishing your deliberation, you finally answered, "I'm open to the idea, but would you mind answering a few questions first?"
"Sure, I can understand the hesitance, so I'm more than willing to help clear any doubts," the succubus replied warmly.
"Okay... So I guess this is probably a common question for you, but is it permanent?" You queried.
Shaking her head, Mona explained, "Not at first, no. When I initially become part of someone, it is possible for the host to reject me and return to normal. However, the more my host climaxes, the tighter our bond becomes."
"I see..." You trailed off before questioning, "Is there any way to predict how you will affect my body?"
Nodding, the other mother replied, "Sort of, yes, though only very generally." Stroking her chin with her upper-right hand, she continued, "It depends on how compatible the host is with me. If they are very different physically and mentally, my features will manifest more weakly or erratically, like with my eyes being on Mary's breasts. However, a stronger compatibility will allow me to grow more naturally and completely on the host. Think like Erika's cocks, except on a grander scale."
"And how would you estimate our compatibility?" You asked, fascinated by how intricately structured this all was.
"Physically, highly compatible," Mona answered, "So the rest will depend on how similar we are mentally."
Intrigued, you realized that this meant you would probably be able to tell very quickly whether Mona would be open to the app's capabilities, and would have a way out if you thought she wouldn't be. Ending your interrogation, you stated, "Okay, I think that put most of my concerns to rest." Speaking with your left head, you offered, "Alright, let's try it."
"Thank you!" Mona enthusiastically responded, "I promise you won't regret this."
Approaching your nearest body, she began using three of her hands to start stroking your dicks while her remaining ones fingered your nipplecunts and original vagina. As she was taking turns kissing each of your heads, you could swear that her kisses were like an aphrodisiac, making you far more aroused than usual. Hungrily, you reciprocated her advances, and before long you both came in unison.
As your bodies divided in two as usual, that same inky, black liquid flowed from Mona into one of your twinned copies. Immediately afterward, all of your innumerable duplicates began to transform as a lavender lump started growing out of your left hip. As it kept expanding, the flesh spread out vertically in both directions, keeping a similar width going up while making a smaller column going down. Before long, enough features took shape for you recognize the lower part as an extension of your waist and a new leg, complete with a vagina in the newly created crotch. Continuing to grow, the upper part formed a toned belly, followed by three sets of generous breasts and arms, until finally a copy of Mona's head and neck got created above the top pair of shoulders.
"Damn, we're way more compatible than I expected!" Mona exclaimed with her new head on the torso attached to one of your bodies. "This is the first time I've met someone similar enough that I got conjoined to them like this." A few moments later, she asked, "Holy hell, just how many bodies do you have? I'm practically getting dizzy from how many new heads I have and all these sensations I'm feeling..."
Chuckling a bit, you replied, "Well, let's just say there are seven commas in that number, rather than take the time to say it precisely."
Counting on her fingers while mouthing the words for each tier of numbers, Mona's jaw dropped as she murmured, "That would be in the sextillions..." Bouncing back quickly, she smirked and said, "I think you and me are going to have a lot of fun together."
As you kept talking with her, and Erika and Mary rejoined the conversation, your body with the phone was off in another room with nobody but more clones of you and your new bodymate. Suddenly, the Mona head on your phone-holding body asked, "Say, did you write that sentence?" Caught off-guard, you looked down to see a new sentence in the app.
"This succubus is enjoying having her torsos attached to each of a hermaphrodite's bodies."
The fact that Mona was asking meant she wasn't aware of the app's history. Taking a gamble since she was apparently very similar to you mentally, you answered, "No, this app generated it."
"Really?" She questioned somewhat doubtfully, "What does it do?"
Figuring it would be better to show instead of telling, you changed the word "her" so that the sentence read:
"This succubus is enjoying having two torsos attached to each of a hermaphrodite's bodies."
Suddenly, reality shifted, and you found a second copy of Mona conjoined to you, this time on your right side. To your surprise, that wasn't the only thing to change, however. Back in the kitchen, Mona's real body changed too, becoming conjoined twins with two whole upper bodies attached to one waist, having three legs and two crotches. Furthermore, each of Erika's Mona-cocks had doubled, giving her four on each upper body. Meanwhile, Mary was affected much less, only gaining a second nipple-vagina on each of her lower two breasts.
Looking around incredulously with equal parts confusion and excitement, your now-doubled bodymate quietly asked, "Did that just transform me... you... us?"
Grinning a bit, you explained how the app worked. After you finished, Mona giddily exclaimed, "That's so amazing!" Already exploring millions of your shared bodies, she was definitely showing you the benefits of being sandwiched between two parasitic succubi. Feeling her fingers pumping in and out of her vaginas, it felt excitingly foreign to have part of your body moving without you willing it, but still feeling every bit of it.
"So..." Mona's head to your left started before her head on your right asked in a sultry tone, "Mind if I try making a change with the app?"
Feeling like you owed it to her to let her have some fun, you answered, "Sure, just tell me what to change."
"Alright, keep it on me and make a new sentence," she directed while continuing to fondle your conjoined form. Generating a new statement, you both saw the following:
"This succubus is fingering her wet pussies."
At her request, you changed "wet" to "tripled". Suddenly, you found that she not only had three pussies in each of her crotches, but your own pussy and nipple-vaginas had also bee ntriplicated. Experimentally reaching your hands up to your middle pair of breasts, you shuddered as your fingers trailed across the three side-by-side slits. Sticking your tongues out, you could also feel that each of them still had three tongues in each as well.
Mona's original body wasn't unchanged either, as both of her crotches also had a trio of dripping pussies in each now. Even her dick-selves got a trio of miniature vaginas, and Mary now found her lower breasts crowded with six nipplecunts each in a two-by-three formation.
Now that it seemed like you and Mona were going to share any changes made to yourselves, your mind swam with the possibilities this presented. And with how openly Mona was accepting this, you could only imagine what the devious succubus might come up with.