https://twitter.com/fuwamoco_en/status/1740984674615541933This might sound weird, but when they post lovey-dovey stuff like this for the ruffians, I imagine them also getting all lovey-dovey and having sex with each other.
Basically, it's because when a girl is in love, the sexual desire builds up, which in absence of her love interest, she would relieve by masturbation. But since Fuwamoco are always together, the sexual need would get directed to each other.
While it might be weird to think how loving the ruffians would make Mococo seek sex from Fuwawa (for example), it sort of makes sense when you think about it.
It comes down to the theory that for Fuwamoco, having sex with each other is more like masturbation for an individual (playing eroge together is completely fine "because we're twins"). As seen before, Fuwamoco get really open and personal with each other, like with the post-stream reflection thing. They are inseparable parts of one unit that wouldn't be able to fully function without both.
It's not so much about Mococo's or Fuwawa's individual relationship paths with the ruffians, it's something they have built together. Since it's a shared relationship, with largely shared feelings, they need to stay up to date with each other's feelings and experiences, which would include fantasizing and masturbation together thinking about the ruffians. "But aren't there differences between Fuwawa and Mococo?" Yes. You have different sides to yourself too, but these sides don't exist in isolation, they all relate to each other, combining into the package that you are. Fuwamoco present themselves as a package, and (most) ruffians accept them as a package with various aspects inside. Them going separate ways with their own secret fantasies would break the cohesion and just wouldn't make sense.
- Evidence of Mococo's neediness towards ruffians getting redirected to Fuwawa:
https://youtu.be/ydD-l-36UHk?t=1352- Also, see Fuwamoco fanart. In fanart, they are always pretty touchy-feely with each other looking at the camera. I strongly feel that it has to do with their love towards the ruffians, eg. the clingier, the more it means they love us. You could brush it off as an yuri+idol trope to make the girls more attractive, but art is still artist's take on the subjects, and it just makes sense.
- You can even see similar thing /here/ with ruffians getting all cozy and faggy with each other, despite us not knowing each other and despite men naturally repelling each other. Considering that Fuwamoco are women, have the closest human bond possible, and are in a shared romantic relationship with us, the scenario of them still NOT sharing and helping with each other's sexual affection towards the ruffians just gets extremely unlikely.