Overall this is an exceptionally promising work! Really well done and I'm very much looking forward to what's next

My rambling thoughts:
A fresh premise with the potential for many interesting and fun developments.
The writing is very solid in my opinion. Though the exposition is ham-fisted, the rest strikes a good balance between erotic and realistic without being cringe.
Katie, Lily and Becca are just perfect - they are my favorite by far. The trio and Becca all have varied personalities and are written befittingly, with each given their own cute and charming moments and traits.
I especially look forward to seeing Lily (+Kudos for giving some tummy love!) explore her fetish and fulfill her wishes, and I wonder if the others have any of their own? 
And I must praise the character design of these fantastic four girls (the Trio+Becca), their faces and proportions are PERFECT, well done! (I will note I did think they are slightly too tall as previously stated here in the thread, but I don't mind that too much with everything else being so well-made)
A plot point that isn't properly explained in chapter 1:
So how not only the trio, but also Becca and Yuna (and probably many more) get infected with PGI-257 without being anywhere near the explosion? And not PGI-255? And if it was actually spread by the explosion, it creates another potential plot hole...
The way the virus works and when it infected the girls is also confusing: Jasmine says the infection requires the victim to recieve semen regularly or eventually die. But nothing is said about the mind-control \ psychological effects some are suffering, like we see when Frank and Becca first meet, and the incestuous desires it instills..? That potentially explains how the Trio fell for Frank, but they claim they fell for him before Tracy died - meaning, before the PGI was supposedly brought in/spread/exploded. It's all rather convoluted
/ISPOILER]