In the future, minds can be backed up, stored, and uploaded as easily as we back up our harddrives now. Most people have, from birth, been given implants or opportunities to expand to different "morphs," all manners of bio-engineered or synthetic shells to house their consciousness. One of the most common implants in this transhuman future is that of the Muse. Muses are often implanted during childhood, and are intended to act as a sort of mentor and companion to the child, and for many, their lifelong companion is as integral to their being as their own personality. While typical Muse implants are nothing more than simple AI, rarely some elect for, or are given, full-fledged consciousnesses in place of the normal AI. While sometimes these consciousnesses are more advanced AI, they are more often actual human minds, stored as data and running exclusively as a Muse, often those whose bodies were lost or destroyed and lacked the means to access another true morph. Known as infomorphs, they can communicate with their host and access their host's sensory information, but without extreme modifications and specific implants, are unable to control the host in any real way.
The idea for the roleplay itself would be that your character purchases or receives a Muse implant only later in their life, and I would take the role of thee infomorph contained within the implant. Born a male, my character was a soldier for most of their life for one of the various hypercorporations that populate the system. Due to this, he has spent most of his "life" in special, gene-modified combat biomorphs known as Furies, which are almost always biologically female. In spite of being male, and still having a male consciousness and outlooks, his mental imprint of his own appearance has taken on the appearance of a Fury, and even as an infomorph, he represents his "appearance" in the hosts consciousness as a female.
As the host and Muse would share an extreme degree of intimacy, I thought this would make for a really interesting romance story; the plot would be very light on smut, though it is entirely possible and could make for some interesting writing. The idea would be that your character may not even realize that I'm an infomorph at first, and it could make for some interesting roleplay later on. Some interesting issues to explore would be the sexuality between an incorporeal consciousness and their host, but additionally, based on your preference, my character could at some point obtain a new morph, either as another Fury or some other form that you're interested in.