The secondary frame are flashbacks into the characters' history to discover what brought them to this mortal conflict. The flashbacks also feature conflict but in the sense of the characters testing and trying to manipulate one another.
Showdown continues to use the two-track theme in the round resolution, where players dice off via the selection of limited hand of cards representing a range of sizes of dice. The highest roll wins but there are two rolls to resolve, the one for the fight and the other for the flashback. The person winning the duel gets to eliminate the other players attack card, forcing them out of options.
The person winning the flashback gains an insight that allows them to understand more about the character and in particular to throw new light on their true character. So if a character had a self-perception of Loyal to my friends the player with insight might narrate the outcome of the flashback to reveal that they are in fact Too scared to leave the gang.
This secondary mechanic is how the game decides who will be seen as the villain in the conflict. Both characters arrive thinking of themselves as righteous but both have their darkness exposed by the violence.
The game mechanisms do not seem to be fair or balanced. Should a player for example win both duel and flashback rolls then the other player will be on the backfoot for the rest of the game. This seems to be intentional as the narrative beats reflect the fact that the duel can only have one winner and there is a need to avoid a long period of losing where agency is being ground away. Sudden reverses from round to round would also presumably be problematic to the narrative.
There are quite a few two-player games that are short and are meant to have a couple of rounds played in a single session. I get the feeling this is one of them.
I bought the book and then the accompanying card set. The cards are small in number but the game uses them in a very specific way that makes it a bit tedious to try and do your own set. The shipping was a little high so I would recommend getting both at the same time if you are purchasing it physically.