Haitoku Pistols is a music artist and group associated with the Monster Strike multimedia franchise, particularly its anime and music projects. The group is known for contributing songs to the Monster Sonic! series, which focuses on musical storylines within the Monster Strike universe.

The most notable credit for Haitoku Pistols is the song UNKNOWN, which was used as an insert song in the anime series Monster Sonic! D'Artagnan's Rise to Fame. This series, which aired from June to July 2017, follows the character D'Artagnan pursuing an idol career in Tokyo. The song UNKNOWN appears in episode four of this series.

Beyond this insert song, Haitoku Pistols has released several other musical works tied to the Monster Sonic! franchise. The group is credited as the performer on a digital single titled Perfect Glory ~Senritsu no Kanata e~ Monsoni! - Single, released on June 3, 2019. This single includes three tracks: Perfect Glory: Senritsu No Kanata E, Unknown, and a piano edition short version of Perfect Glory: Senritsu No Kanata E.

The artist has a catalog of songs that appear on music platforms. These tracks include Nekkyo Euphoria, Onsoku Exist, Wishing, Senko Progress, and No Distortion, with instrumental versions also available for many of these songs. One of these releases is titled Nekkyo Euphoria [Monsoni!] - Single, indicating its connection to the Monster Sonic! project.

Haitoku Pistols is also depicted as a band of characters within the Monster Strike universe. A short original net animation titled Haitoku Pistols no Kinkyuu Kaigi? was released on May 25, 2017, to commemorate the group's live appearance at the XFLAG PARK 2017 event held at the Makuhari Messe International Exhibition Hall. This two-minute comedy short serves as a pseudo-sequel to earlier Monster Sonic! works and depicts the band members meeting at a cafe to discuss the upcoming event after seeing a promotional flyer.

The members of the in-universe band include the characters Ibaraki Douji and Satan. The voice actors portraying these characters are Asuka Nishi as Ibaraki Douji and Shoutarou Morikubo as Satan. The group's musical identity is rooted in the anime genre, with their songs serving as theme and insert tracks for anime productions within the Monster Strike franchise. The band exists as both a fictional group within the Monster Strike narrative and a real musical act that produces and performs songs for the associated anime series.