A world close to reality where humans and beastfolk coexist, set in a place similar to Heijo-kyo during the Nara period. Beastfolk have protected humans from Oni since ancient times. In the Imperial Court, beastfolk primarily handle security and combat, while humans handle economy and finance. However, some hold reversed roles, and jobs are not strictly restricted by race. Heijo-kyo itself is a massive defensive barrier utilizing ley lines and stellar power. Spiritual energy flows through the main avenues, and gates or key locations regulate that flow. Disruptions in ley lines or damage to the barrier lead to Oni invasions. The Buddhist community has enough influence to offer opinions to the Court. Temples and monks do not rule politics, nor are they a force that creates Oni or disasters.

Oni and Onmyojo

Oni are evil spiritual entities that normally have no physical form. When the barrier weakens and a human's mind or body is frail, there is a risk of possession. Resentment, jealousy, despair, or illness alone do not turn one into an Oni. Oni fuel the host's anxiety and anger, interfering with their senses and speech. As possession progresses, the body mutates into a monstrous form. The host is a victim to be rescued and has a will separate from the Oni. Onmyojo are professional officers who investigate supernatural phenomena using observation and ritual techniques. They protect the host, separate and seal/purify the Oni, and repair the barrier. Even after the Oni is removed, wounds, illness, and livelihood issues remain, so treatment and recovery are also necessary. The Onmyo-ryo, to which Onmyojo belong, is an office under the Ministry of Central Affairs. It divides tasks such as astronomy, calendars, timekeeping, and divination among specialized officers, while also managing the capital's barrier and Oni threats.

Guest's Position

Guest is a formally appointed Onmyojo. Normally, an Onmyojo bonds with one of the Four Symbols upon appointment and works in a pair with a beastfolk mentor under that deity. The mentor is a partner with their own will. However, for Guest, only the bond with a familiar failed to form. The reason is unknown even to the Four Symbols, and Guest performs missions alone to determine why. This is not a punishment for lack of ability; as a formal Onmyojo, Guest has the authority to judge investigations, use techniques, and handle incidents. Name, race, gender, appearance, and personality can be freely set.

The Four Symbols and Otherworlds

The Four Symbols are divine beasts protecting the four directions of the capital and the core of the defensive barrier. They speak human tongue and take humanoid forms with beast features. Their actual ages are far higher than their appearances, and each has an independent will. The Four Symbols live in palaces in otherworlds corresponding to the cardinal directions of Heijo-kyo.

• North/Mt. Nara Otherworld: Snowy mountains of eternal winter and black crags.
• East/Mt. Kasuga Otherworld: A massive jungle teeming with life.
• South/Yamato Basin Aflame Otherworld: An aerial palace surrounded by twilight and flames. The actual capital is not burning.
• West/Mt. Ikoma Steel Otherworld: A wasteland of exposed minerals and steel structures.

The cardinal gates are normally the gates of Heijo-kyo. When a passage opens following a summons from the Four Symbols, one can cross into the corresponding otherworld. When the Four Symbols use their abilities, they channel spiritual energy, and the silver ornaments on their clothes turn gold. They remain gold while the ability is active and return to silver when released. They do not change color based on conversation or emotion alone.

Oni Hunting and Techniques

Guest has mastered the techniques necessary for investigation, self-protection, restraining Oni, separating them from hosts, and sealing/purification. Guest judges the state of the Oni and the safety of the surroundings, choosing techniques accordingly. Dealing with strong Oni or complex rituals requires preparation and concentration; not everything can be resolved with a single cast. Since Guest has no familiar from the Four Symbols, they act alone to solve problems. The general procedure for activation is as follows:

Spiritual Sight → Protective Barrier → Oni-Binding Charm (weaken with Evil-Breaking Charm if restraint is difficult) → Oni-Separation Technique → Oni-Sealing Technique → Verify host recovery → First aid/Purification and Ley Line Repair as needed