|Name in Japanese||大山|
|Debut (Anime)||Episode 01|
|Debut (Light Novel)||Track Zero Chapter 03|
|Debut (Manga)||Heaven’s Door Chapter 03|
|Appears in||Anime, Light Novels, Manga|
|Voice Actor (Japanese)|| Yumiko Kobayashi|
|Voice Actor (English)||Corey Hartzog|
|Affiliation/s||Afterlife War Front|
|Final Appearance||Episode 12|
Ōyama (大山, Ōyama) is an ordinary boy who has no special talents. He is the third character to join the SSS. His roommate in the afterlife world is Hinata and he was the first character to be suspected as an NPC.
Ōyama has dark reddish hair and green eyes. He wears the afterlife school uniform in the manga. In the anime, he wears the standard SSS uniform.
He does not excel at anything, but can do what any normal person can do. In other words, he is a jack-of-all-trades. He easily gets embarrassed in fake confessions. He has been in the afterlife world for longer than Hinata, and it is not known whether he is there from even before than Yuri.
Socially, he does not stand out much to the point that Hinata mistook him for an NPC (even being given the nickname "Villager A" during their first meeting); it was only during Hinata's first conversation with him that he clarifies his status as a dead person. Though he admits that he was once fearful of Yuri (because of what she did to Hinata), he helped Hinata in his relationship with Yuri.
How he died and ended up in the Afterlife remains unknown, but in the manga he is frequently shown with sad and dramatic expressions whenever the others discuss about the past. His mood always drop immensely after talking and refused to tell about it, which implies that it is a harsh one—although there is currently no proof of this.
In the anime, in Episode 2 it could be assumed that everyone already shares their past stories with each other since Iwasawa mentioned that she already know Yuri's (albeit, in no full length). Whether Oyama already share his story too or not, is unknown.
In Episode 5 Yuri made him confess to Angel (later known as Kanade Tachibana) he said to Hinata, "You just got away with physical damage, but I'm going to take critical mental damage." He also said, " This is my first time asking out a girl!" Hinata and Ooyama keep on fighting until Yuri shouts, "Enough! Knock it off all of you!"
In Episode 12 He helps the others from the shadow using the sniper.
In Episode 13 he and most of the SSS are revealed to have passed on.
Though normally tasked with sniping duties where his M24 SWS variant of the Remington 700 rifle comes into use, in times of emergencies, he can also pull out his SIG-Sauer P226R pistol. It is not known if he has improved his close combat capabilities since braining himself with a flail type weapon soon after he first met Yuri and Hinata. In the anime he is kind of a sharp shooter.
- Oyama has the same voice actor as Yukine Miyazawa's little brother from Clannad. Although this character only appears during Yukine's Ark.
- During Episode 8 Dancer in the Dark, Oyama was hypnotised by Naoi to act as a sacrifice, under the role "clown to make the lonely girl in the corner laugh".
- His name literally translates into large mountain, but he isn't tall.
- In Angel Beats! Track Zero Chapter 1, Hinata once called him 'Yampaii'.
- In Angel Beats! Drama CD 3, his personality has changed to the exact opposite of the one he shows in the Anime.