Where does senpai come from?
The hierarchical relationships in anime and manga reflect those in modern Japanese society. One of these relationships is that of a senpai and a kohai. Senpai is sometime spelled sempai. The more common transcription of the word is senpai—sempai reflects a mispronunciation that’s the result of the interaction of the n consonant with the following p consonant, causing the n sound, when realized, to shift in anticipation for the p sound. Sempai (though technically incorrect as there isn’t a standalone m sound in the Japanese alphabet) is easier to pronounce. Try to say both senpai and sempai. Which one is easier?
In Japan, senpai is an honorific for an upperclassman or a mentor figure. It’s a reflection of the social hierarchy in educational and professional settings. On sports teams and in businesses a senpai is someone who has been on the team or has been in the organization longer than someone else. In school, a student must be at least a year ahead of a kohai to be considered a senpai.
Senpai may be added to the end of someone’s name or it may be used as a title all on its own. For example, if there were a character named Haru, he could be called either Haru-senpai or just senpai. A senpai is someone a kohai looks up to and aspires to be like. The kohai is an underclassman that a senpai teaches. Eventually, a kohai becomes a senpai when they take on their own kohai as they move up in the school system.
Who uses senpai?
The title senpai is used by the kohai in a relationship as a term of reverence and respect. Characters in anime and manga refer to each other with these titles often when they address one another. People who aren’t junior to a character in question won’t refer to that character as senpai. Instead, they may be referred to with other honorifics, such as -sama, -san, or -chan depending on the situation.
Senpai is often used in the English in the expression “notice me senpai” and its variants. Originally this was used in the context of a person hoping a crush or someone they admire will pay attention to them, but it has more broadly been used online in reference to famous people acknowledging a fan’s existence.
“Oh no, an email for Izumi-senpai. But he already graduated.”
Miyako Inoue, “Yūki o Uketsugu Mono (勇気を受け継ぐ者) (Eng: Enter Flamedramon ("The One Who Inherits Courage")),” Digimon Adventure (April 2, 2000)
“Oh, yeah? Well, at least I HAVE a routine, Tamaki-senpai!”
Haruhi Fujioka, “Fushigi no Kuni Haruhi (不思議の国のハルヒ) (Trans.: Haruhi in Wonderland!),” Ouran High School Host Club (June 27, 2006)
“Cheer up, Saionji...senpai.”
Anthy, “Bara no hanayome (薔薇の花嫁) (Trans.: The Rose Bride),” Revolutionary Girl Utena (April 2, 1997)