Full Metal Panic! Sigma (フルメタル・パニック!Σ) was written by Shoji Gatoh and illustrated by Hiroshi Ueda and focuses on the missions of Sousuke as a sergeant. The first volume was published on August 1, 2005, and the last volume, the nineteenth, was published on September 20, 2013. Its events are based from the fourth Full Metal Panic! light novel onwards.