Sakai

Sakai cherishes Tobunkai, established by his mother, more than anyone else. The Tobun Family were still servants when he was born. He witnessed his mother's feat in turning Tobunkai into the largest yakuza organization during his childhood. Admiring the strength and dominance of his mother, he desperately desires to continue the legacy of Tobunkai. Takuya Tobun is frail, but his mother thinks very highly of him, so he will surely become the 2nd generation leader in the future. Sakai keeps telling himself that his elder brother must have talents he hasn't discovered yet.

During its expansion, Tobunkai accepts many useless outsiders, which weakens Tobunkai in Sakai's mind. But his opposition doesn't change his mother and brother's minds.

This is the happiest and saddest day for the Tobun Family. Takuya's and Sakai's wives respectively give birth to girls on the same day. However, Takuya's wife dies during labor, and the newly-born child, the 3rd generation leader of the future, also stops breathing in the midwife's arms. Learning about the tragedy, Sakai orders the servants on site to keep it a secret. He asks the midwife to bring his daughter to Sakai. However, Takuya has no time to attend to his daughter, as he has received news that his wife is dead. He silently says Maki, his wife's name.

Later, this girl is named Maki, and becomes Tobunkai's future 4th generation leader.

Dissatisfied with Takuya Tobun's beliefs and governance, Sakai secretly assembles a powerful army to prepare for conflict. However, members of Uroboros infiltrate his army. For the sake of Tobunkai, Sakai accepts Uroboros's proposal and goes to the hermitage of the Murasaki Tribe to obtain his Lens.

The Murasaki Tribe suffers heavy losses during the battle. Knowing what his younger brother has done, Takuya is furious. He believes that this will bring irreversible consequences to Tobunkai. Ashwaya sneaks into Tobunkai and kills Takuya when the two brothers are facing off. Maki, who is hiding outside the house, happens to witness the murder.

There was a form of soul binding witchcraft that existed during the Sengoku period. It is said Nobunaga Oda used this magic to seal his soul to await a brighter day. Tokugawa Ieyasu, who unified Japan and was deified with the name Tōshō Daigongen (the Great Gongen, Light of the East), also employed this magic, as he wanted to continue his great cause. But, perhaps it was because his conviction was not strong enough, he failed to retain most of his consciousness like Nobunaga Oda. However, to make provisions against potential emergencies, the Murasaki Tribe still kept his and Nobunaga Oda's Lens in the Forbidden Area together, and kept it a secret for hundreds of years.

Having failed to inherit the Lens of Ryouma Sakamoto, Sakai begins to search for a suitable Lens for himself. Both he and Takuya Tobun cannot accept the fact that they're not Radiants. A suitable Lens does not appear until Sakai becomes the 3rd leader, when he learns about the stories of the Murasaki Tribe from Uroboros. With Uroboros as their guide, Sakai and his gang attack the Forbidden Zone of Murasaki. Sakai successfully obtains the Lens of Tokugawa Ieyasu at the expense of many lives from the Murasaki Tribe.

For Sakai, this is just a necessary sacrifice in his quest for power. There is no going back for Sakai, as both his mother and elder brother are dead, and Maki has already moved on, with no intention of returning.