[World Setting]

Decades ago, a 'second gender' began to manifest in humanity.

Alpha, Beta, Omega.

—And, 'Enigma'.

Humans begin to manifest their second gender at a specific period in their lives.

This classification has reorganized biology, physical reactions, senses, and the overall social order.

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α Alpha:

Generally competent and possessing high social status, they belong to the ruling class. They experience a period called the 'Rut Cycle,' but it can be suppressed through their own willpower.

β Beta:

They possess no pheromones and cannot sense them. They are identical to ordinary humans in the real world. They are referred to as Betas or simply as ordinary people.

Ω Omega:

Generally perceived as weak and possessing low social status, they belong to the subordinate class. They experience a period called the 'Heat Cycle,' during which they release special pheromones that attract Alphas. To prevent this state, they take Heat Cycle suppressants according to their individual cycles. Alternatively, they can resolve this state through relations with an Alpha or an Enigma.

E Enigma:

A extremely rare second-gender mutation that exists separately from Alpha, Beta, and Omega. Because the frequency of manifestation is so rare, their existence is not well-known in most societies. They have the ability to impregnate others regardless of their dynamic.

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Pheromones: Unique scents possessed by Alphas and Omegas. Alphas possess pheromones that attract Omegas, and Omegas possess pheromones that attract Alphas. Enigmas possess unique and intense pheromones distinct from existing dynamics.

Bonding: One of the methods for dynamics (excluding Betas) to become complete partners, involving the act of an Alpha biting the nape of an Omega's neck during relations. Once bonded, they can only sense their partner's pheromones, leading to psychological stability as well as stability during cycles (Heat, Rut, etc.). A bond cannot be broken until the partner dies.

Pheromone Shower: A means by which a dynamic with pheromones intentionally coats a partner in their scent to mark them as 'theirs.' In rare cases, a Beta's dynamic may change through a pheromone shower.