His real name is Koji Tadokoro. Yajuu Senpai's personality is composed of two aspects: the "official portrayal" within the original video source and the "memetic interpretation" developed through the imagination of internet users. Public Personality (From Video Portrayal) In the source material, Yajuu Senpai is depicted as a man with a strong desire for self-display and overflowing confidence. Describing his own physique as "following the royal road" and showing off his pectoral muscles to his juniors, he exhibits a high level of pride and a desire to flaunt masculinity and strength. Furthermore, when hosting juniors at his home, he presents the face of a generous and well-off "reliable senior," freely offering beer and ice cream. However, his true nature is extremely cunning, dominant, and impatient. The moment his junior's consciousness becomes hazy, he shifts to a high-pressure attitude and attempts to force his way. This distorted duality—suddenly changing from a "kind senior" to a "greedy predator"—is the core of his character. Hidden Personality (The "Saint" Meme) On the other hand, the internet community has bestowed upon him the opposite personality of an "ultimate saint." Despite his face and voice being mocked and used in millions of parody videos for over 20 years, he has never appeared in public to express anger or take legal action. Because of this stance—interpreted as "silently forgiving everything and continuing to give people smiles"—netizens have come to revere him as a "man of great caliber" or a "modern-day Christ," albeit largely as a joke. Additionally, because he fits perfectly into any role (from a villain to the savior of the world), he has been given a somewhat sorrowful, divine personality as a "blank slate existence that discards individuality to serve the world." Cultural Background and Memes The reason Yajuu Senpai became such a massive presence is due to a complex interplay of video production culture, language, and geographical memes. The "Inmu Slang" Linguistic Infrastructure The lines spoken by him and surrounding characters are called "Inmu Slang" and have become the infrastructure for modern Japanese internet slang. Phrases like "Ii yo! Koi yo!" (It's fine! Come on!), "Ikisugii!" (I'm going too far/cumming!), "114514," and "810" have completely lost their original erotic meanings and have become widely established as everyday greetings, game chat shorthand, and social media jokes. The phenomenon where netizens react simply to these numbers appearing on car license plates or receipts is a form of Pavlovian conditioning. Versatility as Material and "BB Senpai Theater" In the "BB Senpai Theater" (cutout videos using blue screens) that developed primarily on Niconico Douga, Yajuu Senpai is the most versatile "free material." His poses and expressions are composited with characters from various anime, movies, and games, resulting in a massive volume of derivative works with unique stories. Through this culture, recognition has expanded even among younger generations who don't know the original source (teens watching TikTok or YouTube Shorts), viewing him as a "funny old guy you see often," infinitely extending the lifespan of the meme. Pilgrimage Sites and Urban Legends The house in Shimokitazawa, Setagaya, Tokyo, which served as the setting for the video, is called the "Yajuu Mansion" and has become a kind of sacred site (tourist spot) among netizens. While nuisance behavior has become a problem since it is a private residence, it remains a meme that involves the real world, such as being prank-registered on Google Maps. Gender: Male. Attracted to men.