Kazuma/Synopsis

History
He was born as the second son to a salt wholesaler and was chosen to inherit the business but was murdered by his brother at the age of 19 just before the ceremony.

Kazuma is the last of Vaisravana's (Bishamonten) "old" Shinkis. At one point, (and without Vaisravana's knowledge), he requested that Yato dispose of all of his brethren, as they were corrupt and infecting their master with Blight. Heeding his request, Yato slaughtered all of the Shinki, (with the exception of Kazuma). This left Kazuma as the last survivor of the "Ma Clan". This would also spawn the lifelong hatred Vaisravana would possess for Yato.

Story
In his debut, Kazuma is seen speaking to Vaisravana about Yato. Later, he is seen in his Shinki form, tracking Yato and Yukine and navigating for Vaisravana. When Vaisravana catches up to Yato and Yukine in the forest, Kazuma reverts back to his human form, tending to the injured Kuraha, (who was harmed by Yukine). He then stops Vaisravana from pursuing Yato, after Kofuku had opened the Vent with Daikoku, telling her it was too dangerous, and that while she might want to give chase to Yato, he would not allow her to risk harm to her Shinki further. Vaisravana, seeing reason, departed. Before Kazuma fled, he bowed to Yato, then disappeared.

Later, when Vaisravana was searching for Yato, and Phantoms who had escaped from the Vent, Kazuma spotted Hiyori Iki. He spoke with her, hiding her from Vaisravana and Kuraha, and voiced his concerns on Yato's deteriorating condition. He mentioned that Yukine would soon have to be dealt with, for his crimes against his master, and asked Hiyori to look after Yato. With her agreement, he departed, but not without warning that, if Yato's Blight spread further, he would die.

Hiyori arrived at Vaisravana's temple, in search of Kazuma to help with Yato's Purification Ceremony. He agreed to assist, arriving with her at Kofuku's shop. He, alongside Mayu and Daikoku, began the ceremony. However, halfway through it, as Yato's condition worsened and Yukine began to become more and more corrupt, he urged Yato to break his contract with Yukine, and for Daikoku to kill the Shinki. However, the ceremony was a success, and Kazuma departed soon after.

When Vaisravana's own Blight began to spread, due to her neglect of her Shinki, he demanded that all of her Shinki be searched for signs of corruption. Despite this, no signs of such symptoms were discovered, and he later apologized to Kugaha for causing such a disturbance.

Later, Yukine arrived at Vaisravana's temple, in search of Suzuha. When Vaisravana spotted him, they soon got into a heated confrontation. Kazuma defended Yukine, and when Vaisravana asked him if the rumors of his involvement in Yato's Purification Ceremony were true, he admitted that they were. Vaisravana, distraught, asked why he had betrayed her for their enemy, to which Kazuma countered that Yato was their "benefactor". Vaisravana attempted to shoot Yukine, but the latter was defended by Kazuma, who created a Boundary between them and his master.

Vaisravana nearly excommunicated Kazuma; however, she hesitated and then exiled him. After being exiled, Kazuma goes to Kofuku's house because it is the only place he knows where to stay. Afterward, while Kuguha tries to kidnap Hiyori Kazuma intervenes. He tries to use bind on Kugaha but it is ineffective and ends up getting kidnapped as well.

Upon deducing Kugaha's plot to drive Yato into killing a weakened Bishamon due to supposedly kidnapping Hiyori to spite Yato, Kazuma, and Hiyori attempt to escape the confines of their cell, to no avail. Aiha is able to free them with the help of other Regalia she confessed her sins too. Kazuma manages to intervene during Bishamon's near-fatal blow to Yato, revealing his betrayal of the Ma clan.

He later recovers after Bishamon has banished Kuguha and destroyed the Phantom released by the doctor. He is asked to be her Exemplar once more, even participating in the journal she has made to better understand her Regalias.