Nazca Corporation

R-Type II's graphical style bears great similarity to what this team is known for. However, it is generally thought their first game was Air Duel; they would later make games such as Armed Police Unit Gallop, Undercover Cops, Pound For Pound, Ken-Go, and In the Hunt. Their final game for Irem was GunForce II, after which they left and created Nazca, creating Neo Turf Masters and Metal Slug; the latter shares many stylistic similarities to the previous Irem works and both titles were made with the same development kits used for several Irem arcade games. SNK, impressed by the success of Nazca's titles, formally acquired the developer, and would make the second and third Metal Slug games. The team disbanded after SNK filed for bankruptcy in 2001.

Nine of the original Nazca staff (including planner Meeher, designers Akio and Susumu, and development manager Kawai) answered questions from an undated text interview that was translated and included in Metal Slug Anthology.

Because the common use of pseudonyms in arcade titles to hide identities, details of its staff remains scarce. One known key member is composer Takushi Hiyamuta (credited with names such as "HIYA!" and "HIYA-UNIT"), responsible for composing nearly every game listed here, in whole or part (he did not compose for Kaitei Daisensou; also, although he did not compose for R-Type II, he did for Super R-Type). He was considered part of SNK's in-house band, the "Shinsekai Gakkyoku Zatsugidan" ("New World Music Acrobatics"). He was interviewed for the Metal Slug Complete Sound Box released in 2008. The only works he is credited for since Metal Slug 3 are Yuusha 30, and producer on Sammy Corporation's Dolphin Blue, a credit he shares with fellow Nazca staffer KOZO. He currently works as a freelance musician, serving as the lead guitarist in the rock band GRowTH.

Graphic designer Akio worked for SNK after their bankruptcy in 2001, serving as the lead character designer for Metal Slug Anthology, and as character designer for Metal Slug XX. His final involvement with the company was the design of Metal Slug protagonist Marco Rossi for 2010's Neo Geo Heroes: Ultimate Shooting, released a few months after Metal Slug XX. Other contributions he made directly for the company are currently unknown. He currently works as a freelance artist, remaining fairly active on Japanese art website Pixiv, and has contributed illustrations to Mobius Final Fantasy and Street Fighter V: Arcade Edition. He created a Twitter account in early April 2023, and would later begin to post design documents from Metal Slug.

Kazuma Kujo, credited as KIRE-NAG in the first Metal Slug, went on to form Granzella after leaving both Irem and Nazca, but declined to comment on the status and identity of key staff members including lead designer Meeher and graphic artists Akio and Susumu. While he was responsible for the design of the gameplay, he left Nazca prior to Metal Slug's release due to internal disputes but has maintained friendship with the developers.

In May 2023, Akio Oyabu, Meeher, Kuichin, Takushi Hiyamuta and Shinichi Hamada reunited and announced they are developing a spiritual successor titled Black Finger JET for Steam under Kodachi Studio, with Märchen Forest developer Shinano Ishiguro serving as director.