|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 to be an NPC.
He 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 can do anything, but he will not be the best at it. 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.
At first he was thought by Hinata to be an NPC who he called "Villager A" which was inspired by NPCs in role-playing games; this assumption was dispelled when Hinata discovers that he knows that he is dead. Though he admits that he was once fearful of Yuri (because of what he did to Hinata), he helped Hinata in his relationship with Yuri.
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.
- 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.
- During Episode 5 Favorite Flovar, Oyama was order to ask Kandae out on a date