Keiji Ochiai


 * This article contains plot spoilers from the manga that have not been revealed in the anime. Proceed at your own risk.

Keiji Ochiai (落合 慶司) was an associate professor at Keio University who majored in urban geography. Although he is married with two children, he had multiple relationships with his students. It wasn't until he set his sights on Tsukasa Taira that he was accused of sexual assault and fired from his position.

Appearance
Ochiai is an adult man with purple eyes and an average build and height. He has black, lower-chin length hair and a straight hairline with middle-parted bangs and long locks framing his face. He also has a small goatee. After the timeskip, he is often seen with a gas mask. He also grew his hair out, now being shoulder-length, and he gained a few scars on his face as well.

Personality
Ochiai was initially portrayed as being a kind and considerate, sometimes scolding, teacher. He cares about his students and is serious about their studies and education. He is also energetic and a bit carefree, as he didn't really mind that Tsukasa borrowed one of his books for six months. He said she could borrow his books for as long as she wanted if it leads to a good thesis.

However, underneath this what so appears to be a facade, he has a twisted personality. He had multiple relationships with his students, and he began kissing and touching Tsukasa without her consent. He claims that he thinks that silence is consent, and proceeded to continue assaulting her until Yuuki Anzai arrived. Ochiai seemingly has a very low loyalty, as he cheated on his wife multiple times and also betraying his kids. He said that this didn't really matter to him.

After the following incident, Ochiai got fired from his work and his life turned upside down. This made him become even more twisted and he also became an anti-devil extremist. He is very ignorant and careless as he sees them all as monsters and knows that they will commit crimes sometime, which is why he tries to kill them, even innocent ones. Ochiai is also sly, as he takes devils weakness with blood to make the incident look like the devil is guilty.

He is very confident about his own claim that Yuuki had sex with and then killed Tsukasa, and was very happy about that thought. However, he admitted he was a bit disappointed that Yuuki had "killed" her, since, as he claims, he wanted to rape her before she was "killed". Ochiai is seen to be not one bit ashamed of his own actions, and actually takes pride in them and enjoys provoking people and start fights.

Story
Ochiai was originally an associate professor at Keio University. He was also married and has two children.

One evening, Tsukasa goes to Ochiai's office to return a book she had been borrowing. Upon seeing snow on Tsukasa's hair, Ochiai brushes it off and hugs her. Tsukasa's creeped out by how familiar he's acting, but she passes it off as overthinking. He invites her in to warm up and have some tea. He even offers her another book to borrow. As he hands it to her, he kisses her and continues his advances by opening her shirt and lifting her bra. Tsukasa desperately smashes a mug against a window pane and begins to bleed. Ochiai scolds her for her reckless actions and says that she should've said if she didn't want to do it with him. Tsukasa is horrified since he is married with kids, but he shows no sense that what he's doing is wrong. Yuuki, who was waiting for Tsukasa, sees blood on the smashed window, jumps up to the window and kicks it in when he sees what Ochiai is doing. Seeing the blood, he also transforms and realizes that Ochiai is behind all of it, in which he proceeds to punch Ochiai repeatedly with all his might and fractures his skull. Tsukasa pulls him back to prevent him from killing him. Yuuki flees and Ochiai, in a near-death state, immediately received medical attention.

Following these events, he got fired from his job and position, his wife divorced him and he had to pay her a lot of consolation money. One of his students also spread his personal information on the internet, which ruined his reputation, both among his acquaintances and society. Since his whole was ruined by Yuuki who happened to be a devil (hybrid), he became an anti-devil extremist who aimed to exterminate devils on his free time. Something he hoped more than anything was to meet Yuuki again to get back at him someday. When he did, he attempted to provoke him and bring back all the past memories, which led to him eventually losing control while one of Ochiai's accomplices drags him into the next car just in time. Yuuki bangs on the door, but is unable to break through. Due to the confusion in the whole situation, being in a public place, Ochiai was able to get away.

Etymology

 * The name Keiji means "congratulate, celebrate" (慶) (kei) and "officer, boss" (司) (ji).
 * Keiji's surname Ochiai means "fall, drop, come down" (落) (ochi) and "fit, suit, join, 0.1" (合) (ai).