The Orphan First Kill is not based on a true story. It's a work of imagination crafted by the filmmakers and writers to thrill and engage the audience.
As there is no clear information about this 'orphan first kill real story', it's difficult to define the main plot. However, generally speaking, if it's a real story, it might involve an orphan facing difficult circumstances such as abuse or neglect, which could lead to a situation where they are involved in a killing incident. This could be a complex story with social, psychological, and ethical aspects to consider.
I'm afraid I haven't heard of a particular 'orphan first kill real story'. It could be a very specific incident within a certain community or a story that is not widely known. Maybe it's a made - up or very niche tale. Without more details, it's hard to say much about it.