Yuudai Saejima

Yuudai Saejima (冴島 雄大) was Minoru and Akane's former high school classmate at Sakurazaka Senior High. Following the fall of Japan to Magical Beasts, he became the Vice-Commander of the Knights in the human settlement of Messiah.

Appearance
Yuudai was a young adult with short black hair and facial hair whilst wearing a black shirt with a necklace under a Sakurazaka Senior High uniform as his Messiah uniform. It should be noted that he was often referred to as a gorilla due his bulky physique and expertise on Judo. He was also considered handsome by many students at his high school.

Personality
Not much was known about Yuudai's personality when he was a student. However, as a Vice Commander for the Messiah, he was a blunt man who would abuse his position in attempt to be in a relationship with Akane even going as far as to blackmail her to do as he says.

Background
Former student of Sakurazaka Senior High and classmate of Minoru and Akane, He was a member of the school's Judo club and competed in the nationals before Japan was invaded by magical beasts.

The Birth of the First Knight
Not much details were given of his whereabouts during the birth of the First Knight. However, he was aware of the identity would use it as leverage against her when possible. Sometime after the destruction of Arcadia, Yuudai would rose up into the ranks of the Messiah to Vice Commander and would eventually be bribed into the Alliance as their mole by Yuuka.

Reunion
After Akane took Minoru into her care, Yuudai introduced himself and chastised her for taking him in and suggested that they should've left him for dead. The conversation between the two grew tense after the suggestion as Yuudai remind her of their positions within the ranks of Messiah and reached a breaking halt when Akane protected Minoru from him. However, this would anger Yuudai as he reminded her of the First Knight much to her denial.

Sometime after, Yuudai would break into Minoru's room and accuse him of being a spy. He attempted to "interrogate" him until Akane stepped in and stop him. Yuudai leaves the room and remind Akane that they'll have a emergency meeting later. During the meeting, Yuudai would be shocked to see photographs of dozens of mangled magical beasts and demanded to know who would do such feats. Initially Haitani deducted that the First Knight was responsible but concluded that there was another Knight that was as strong as her much to their relief.

During a magical beast stampede, the Messiah Knights were overwhelmed and Akane would almost be killed until Shadow who took on the alias "Black Knight" saved her and the group much to Yuudai's ire and suspicion of his affiliation. Yuudai would slip off to the back of Sakurazaka Senior High to meet up with his Yuuka regarding intel she gave him but was caught off guard and killed when the double agent by shooting him.

Skills and Abilities
Yuudai was noted to be an expert at Judo as Minoru recalled in his past life that he was the in the school's Judo club and even competed in the nationals before the magical beasts invaded Japan. He was also a proficient fighter and can use magic though not to the extent as members of the Crimson Order or Shadow Garden.

Akane Nishino
Akane's former classmate, she saw no appeal in him and despised him for how he looked at her sexually since their time as students. However, this does not stop Yuudai as he often tried to pursue a relationship with her but to no avail. Whenever the two argue or angered, he would often abuse his position and blackmail her under the threat of her remembering her time as the First Knight much to her anguish.

Yuuka
Fellow double-agent for the Alliance, Yuudai was bribed into their side as their mole in the Messiah until Yuuka murdered him after successfully fending off an magical beast stampede and she got what she needs. She would also exploit Yuudai's death in attempt to frame Akane as a murderer.

Haitani
Much of their interactions are unknown during Shadow and Beta's time on Earth. However since Haitani was the Commander of the Knights of Messiah, Yuudai would be outranked and would follow orders under him.

Akira Nishino
Scientist for the Messiah and Akane's brother, Akira was unaware of either Yuuka and Yuudai's antics until his death.

Minoru Kagenō / The Black Knight
Former classmate of his late incarnation, Minoru was able to recall Yuudai in his past life as he was affectionally referred to as a gorilla and expertise on Judo. When Akane took Minoru in under her care, Yuudai tried to leave him in a monster nest to eaten by monsters until Akane protected him. Yuudai would also tried to use Minoru as a scapegoat when he accused him of being a spy only for Akane to step in to protect him once more.

Natsume
Although the two has never interacted, Yuudai has acknowledged her potential as a possible knight within their ranks and suggested that Akane should've simply taken her instead of the both of them in much to her ire.

Trivia

 * Yuudai was one of the only known students of Sakurazaka High School before the invasion. The others would be Akane and Minoru.