Those were the days An old, forgotten /a/ meme that came from Higurashi fanart of Tsumihoroboshi-hen, the second "answer" arc of the game and the most loved arc of the whole series. At the conclusion of the arc, K1 and Rena had an epic night fight atop the roof of the town schoolhouse (commonly known as the Heaven or Hell fight) - most of the fanart of this duel showed K1 and Rena enjoying the heat of battle, though the fight was quite serious and the tone of the story quite dark until this point. Because K1 and Rena grew to love one another (especially in this particular arc, where Mion got shafted) Anonymous interpreted the fight as an expression of sexual intercourse, and prior to the anime's airing much interest was generated in the final fight. Because of their history of bloody murder and large body counts, the duo started to be called a "Happy Couple", because despite fighting one another their love was so intense they couldn't help but smile.
Stop posting blank images! A character from Higurashi who can only be perceived by Rika Furude. As such, a relatively unfunny and forced meme has arisen in which users post pictures of Hanyuu, and engage in small shitstorms about posting blank images/backgrounds or something similar (implying Hanyuu is in the picture, but no one can see her).
The reverse version occurs when someone actually does post a totally blank picture, usually with the filename of "hanyuu"(or some variation thereof). People then start posting as if the blank images had non-worksafe pics of Hanyuu, usually replying with the promotion meme.
Both of these previous trends stopped as soon as Hanyuu became visable and tangible in the anime.
She is sometimes referred to as "Piss-tan" in an effort to troll Hanyuu fans. The origins of this name stem from a picture showing a...