Translation guide
In Japanese, the term for 'non-player character' is commonly borrowed from English as NPC (エヌピーシー), but there are also native Japanese terms used in gaming contexts. The choice depends on formality and medium.
Referring to a character controlled by the computer rather than a player
The most common and natural way to refer to a non-player character in Japanese gaming contexts. It is an initialism borrowed from English and used as a noun.
このNPCからクエストを受けられます。
You can accept quests from this NPC.
NPCに話しかけてみてください。
Try talking to the NPC.
The full borrowed term, literally 'non-player character'. It is understood but less commonly used than the abbreviation NPC. It may appear in formal or technical writing.
ノンプレイヤーキャラクターの行動パターンを設計する。
Design the behavior patterns of non-player characters.
A shortened form of ノンプレイヤーキャラクター, used in very casual or slangy contexts among gamers. Not standard.
あのノンプレイヤーキャラ、強すぎない？
Isn't that non-player character too strong?
Referring to a character controlled by the game master rather than players
In tabletop RPG contexts, the full term is often used to distinguish from video game NPCs, though NPC is also common.
GMが操作するノンプレイヤーキャラクターが登場する。
Non-player characters controlled by the GM appear.
Also widely used in tabletop RPG circles, especially in casual conversation.
このシナリオのNPCは全員エルフだ。
All the NPCs in this scenario are elves.
Describing a real person as if they were a background character in a game, implying they have no independent will or importance
The term モブ (from 'mob character') is used in Japanese to refer to background characters or extras in anime/manga/games. It can be extended metaphorically to describe a person who seems like a background character in real life. モブキャラ is a slightly longer form.
彼はクラスでは完全にモブだ。
He's totally a background character in class.
自分がモブキャラに感じる。
I feel like an NPC.
Younger Japanese speakers familiar with gaming slang may use NPC metaphorically to describe someone who seems to lack free will or individuality, similar to English internet slang.
あの人、まるでNPCみたいに同じことしか言わない。
That person only says the same thing, like an NPC.
In Japanese gaming culture, NPC (エヌピーシー) is the default term. Using the full ノンプレイヤーキャラクター may sound overly formal or technical in casual conversation.
NPC refers specifically to non-player characters in games, while モブ (mob) refers to any background character, often in anime/manga, and can be used metaphorically. Do not use モブ to mean a literal game NPC unless it's a generic background character without interaction.
この村にはNPCがたくさんいる。
There are many NPCs in this village.
アニメのモブシーンを描く。
Draw a crowd scene for the anime.