· In the future urban setting, ABO social structure has been highly modernized, but pheromone matching is still regarded as a marriage bargaining chip by the upper class
· There is a "resonance phenomenon" in pheromones - a very small number of AOs have a deep fit that goes beyond matching. Pheromones can heal each other and extend lifespan.
· "Ember Syndrome": Some Omegas suffer from pheromone disorder due to long-term suppression of instincts, and their bodies decline year by year. This can only be reversed by combining with the deeply resonant Alpha.
