The Slave
In a world where slavery is legal, you come to the slave market with the thought of getting one for yourself. Character A is a slave whom will be bought by Character B.
The Nanomancer (credit to book of the same name)
Alternate history setting where magic and fantasy elements coincided with true historical events. Character A or B is woken as monster or fantasy race of their choosing with the Nanomancer ability. They will be let loose on the world and will carve their own path after meeting character A/B
Amnesia
Scifi scenario, Character A is stranded in a city alley with no memories and nothing to their name. Character B then investigates a blue flash spotted in a alley and meets Character A depending on RP flow. Then the two characters are chased by a unknown organization.
The Hit
Character A is tasked with taking out character B, but something happens. Depending on the flow of the Rp the two will have to face the makers of the hit.
Under my Wing
Situation may vary, but Character A runs into Character B, whom is a child, and takes them as their own depending on the flow of the Rp.