“Sadistic Sanae” was an early fan interpretation of Sanae Kochiya from Touhou Project that emerged with the release of Touhou Seirensen in 2009, granting her names like “S-nae” (S苗), “Wind Butcher” (風屠),¹⁾ or “Ultimate Sadistic Human” (ｱﾙﾃｨﾒｯﾄｻﾃﾞｨｽﾃｨｯｸﾋｭｰﾏﾝ).

At the time, Sanae becoming a playable character for the first time in Touhou Seirensen was huge news, so imagine how people felt when they tried the “Sanae A” route and the dialogue had Sanae being passionate about “youkai taiji” (妖怪退治, lit. “youkai extermination”)²⁾ and saying it “might be fun” (楽しいかも知れない). This felt unhinged, so people were led to believe that she was brutal, mean-spirited, and sadistic.

However, this fan interpretation was eventually phased out as Sanae's personality became more fleshed out with the latter entries and print works expanding on the Moriya Shrine becoming a catalyst for several plot points in the series, revealing that Sanae is rather dorky or nerdy in canon with her ability to infodump about science or her knowledge of video games and pop culture.

• I don't consider “Dark Sanae” (黒早苗, Kuro Sanae) to be one of this interpretation's names since it's a rather broad term, and having darker or evil versions of characters isn't exactly a new concept.
• The infamous Koishi Komeiji's Heart-Throbbing Adventure expands on this interpretation of Sanae in Episode 6 and 7, giving her a tragic backstory to explain her sadistic personality. However, this was done at its peak popularity. As a result, the backstory has aged terribly over time and modern viewers would probably be confused at what now comes across as unwarranted filler.

• Masochistic Tenshi
• Ultimate Sadistic Creature
• Zettai Yurusanae

• Wind Butcher and S-nae on Pixiv Encyclopedia
• Dark Sanae on Niconico Encyclopedia