Yasumasa Sakakibara (榊原 康政, Sakakibara Yasumasa) was a student of Mikawa Academy and was the school's student council secretary. He was also a member of the Four Heavenly Kings of the Matsudaira. After graduating, he remained in Mikawa until the night of April 20, 1648, when he suddenly disappeared without a trace. His disappearance is later connected to the Lost Nobles incident.
During his days as a student of Mikawa Academy, Yasumasa was an introvert who calls himself as someone "who has zero friends". In contrast, Tadatsugu holds on to his ideology that "everyone is his friends". This clash of beliefs kept Yasumasa from being in good terms with Tadatsugu at that time.
He was known for having a contract with a god of literature with a considerably fierce vigor, and because of this, Yasumasa earned the nickname of "Manifesto".
The Last ReunionEdit
During the resupply of the Musashi on Mikawa, Sakakibara joins Tadakatsu Honda, a fellow member of the Four Heavenly Kings, to meet up with Tadatsugu Sakai, the academy president of Musashi Ariadust Academy. What seemed to be a simple reunion for the three remaining members of the Four Heavenly Kings turns out to be more serious for Yasumasa, as he informs Tadatsugu about what happened to Naomasa Ii, the fourth of the Four Heavenly Kings, who was spirited away during the Lost Nobles incidents.
Sakakibara would later join his colleague Naomasa Ii as he would also be spirited away that night. The only trace left by the spiriting away was a Nikyou Crest in Yasumasa's study, accompanied by the phrase "What do you know?" (何をしているの, Nani wo shiteiru no) written in blood. Despite what happened to him, Yasumasa was able to deliver a pile of documents to Tadatsugu through an automaton. These documents are later revealed to be connected to a certain Genesis Project.
- Yasumasa's appearance has never been completely shown or described in the light novels. Thus, his character design is original to the anime series.