What criteria/themes from Yojimbo are you using?
Two warring factions;
Locals are distrustful of the protagonists;
The factions combined control most businesses in the city;
The protagonists are outsiders from where the module takes place;
The only ones willing to help the protagonists are themselves outsiders;
A member of one of the warring factions has an extremely advanced weapon that they have a near fetishistic relationship with;
The individual members of the warring factions are incompetent and despicable, the real danger comes from their numbers;
The warring factions can be played against each other;