東方事変 or touhoujihen are a Touhou arrangement circle made up of vocalist and lyricist IZNA who handles the illustration and design side of things (excluding their first album) as well as arranger NSY who plays guitar, bass and handles the sound engineering side of things. Before founding a circle together members IZNA and NSY had been collaborating together for some time, they began honing what would become touhoujihen's arrangement style almost 3 years prior to it's first release while the two were collaborating under the circle Sally. While only NSY is an official member of Sally both NSY and IZNA have appeared on every album by the circle, it was through their collaborations under Sally that the foundation for touhoujihen was laid as the duo would create one song for every album by the circle. touhoujihen's arrangements can be described as more colorful when compared to the arrangement style the due presented with Sally, their arrangements will often make use of bright melodies usually but not always played over keyboards and lighter choruses to compliment NSY's previously established Rock arrangement style.
The circle's name (touhoujihen) is inspired by Japanese band Tokyo Jihen who's music is also a source of inspiration for the circle.