As far as I can tell, they're all bi. In Hyperdevotion Noire, the never-appearing player character functionally dates her while also setting her up with a harem made up of basically every other playable character.
Their sexual preference more or less varies by dimension though. The Noire in Ultradimension is shy of being called a lesbian when everyone else was falling for that male silhouette, and the one in Gamarket is a completely different Noire with different "adjustments" distinct from every other iteration.
Really, any one of us can make a fanfic of a completely new, made-up world where the girls are neither lesbian nor bi because it's a rather flexible universe.
Besides, the image may as well been originally Noire and Mayuri, with the guy being pulled along by the latter, making the former angry at him for ruining the peace...
Their sexual preference more or less varies by dimension though. The Noire in Ultradimension is shy of being called a lesbian when everyone else was falling for that male silhouette, and the one in Gamarket is a completely different Noire with different "adjustments" distinct from every other iteration.
Really, any one of us can make a fanfic of a completely new, made-up world where the girls are neither lesbian nor bi because it's a rather flexible universe.
Well, Everyone is Bi already allows for all of that, it's just that you only have to say this character happens to be attracted to this particular character this time. (After all, maybe Noire in Ultradimension is just attracted to a different body type of guy, and that's why she didn't go for the silhouette? Considering she practically instantly goes for a nebulous AFGNCAAP protag whose only substantiated traits (that is, ones the developers assumed about their audience) are being a heterosexual male, a gamer, and someone who looks up to Noire as, well, a Goddess, it's probably safe to assume her preference in men is... well, let's just say the stereotypical Neptunia gamer.
Well yeah, there not a guy there and as on HDN PP they can summon human(male or female) to they wanted to I believe they all bi, they can't just rely on just themselves if they want offsprings