The Holy Sol Temple (聖陽教会, Seiyō Kyōkai) is the dominant religion of the Tokyo Empire, where Sisters, Priests and Monks worship the Sun God. As a result, The empire's sovereign Raffles III is closely tied to the religion.
The Holy Temple teaches that the Great Disaster burned away the culture of the world. Raffles I eventually found the Adolla Burst and used its power to Amaterasu, which allowed the Tokyo Empire to become a safe haven for humans. After this point, Raffles would return to his wife and found the Holy Sol Temple. However, his wife noted that his behaviour changed dramatically upon returning. It is revealed that he was replaced by Yona, who founded the church to serve the Preacher.
Following the outbreak of Spontaneous Human Combustion, The Holy Sol Temple became one of the three organisations that formed the Special Fire Brigade and members of the church pray for the souls of Infernals upon death. The 1st Special Fire Brigade is vastly composed of members from the organisation. Due to the Tokyo Empire's belief that only the Holy Sol Temple can provide medicine, the medically focused Special Fire Force Company 6 is also one of the Temple's constituents.
Some time after Hibana and Iris joined, the church they lived in caught fire and incinerated all the sisters except for the pair as the result of Spontaneous Human Combustion. The two surviving sisters fled, with Iris remaining part of the church while Hibana left to pursue her own goals.
In Year 184, the Temple's shadowy assassins observed the fire in the Kusakabe household. This group aimed to locate and kill the abducted Shō Kusakabe, but failed.
In Year 198, the priest of The Holy Sol Temple and two other church members attended the Rookie Fire Soldier Games, alongside other important figures. The heart of the church is later assaulted by Benimaru and the criminal, Joker.