Manatsu no Yo no Inmu (真夏の夜の淫夢, lit. "A Midsummer Night's Lewd Dream"), or Inmu (淫夢) for short, is a series of memes that spawned from Japanese gay porn videos. The titular video was released in 2001 by Coat Corporation, but the term has expanded to include other works by other companies like Acceed, Samson Video, etc.
The meme originally started around mid-2005, after the Japanese baseball player Tadano Kazuhito was involved in a scandal after his past identity as one of the gay porn actors in the original Inmu movie was leaked. Leading to his dismissial from the Japanese baseball league and subsequent move to the United States.
It's often paired with Gachimuchi Pants Wrestling (Wrestling Series) and Shit Soup Technique (Yaranaika) as the "Holy Homo Trinity" (御三ゲイ) since all three were well-known homoerotic memes that were popular within Japanese communities in the 2000s. However, when Niconico emerged in the late 2000s, it was considered an arch-enemy of Gachimuchi and fans would often flame each other's videos. While Gachimuchi would become popular internationally and more recognized after several Gachi MADs were uploaded (and re-uploaded) on YouTube, it would later be supplanted by Inmu on Nico Nico Douga and within the Japanese community after more videos of Yajuu Senpai were uncovered around the 2010s.
Fans typically refer to an actor in one of the works by an initialism of their name (e.g. Tadano -> TDN, Yajuu Senpai -> YJSNPI, etc.) with either "Aniki" (兄貴, lit. "Big Brother") or "Aneki" (姉貴, lit. "Big Sister") attached to them at the end, corresponding to the actor's gender. This is called "TDN Notation" (TDN表記).
Inmu is often linked with the Cookie☆ series of Touhou memes, after they latched onto the original video that started the meme (even coining the name it now uses), and the developments thereafter relating to said video.
