A Factor in the Special Task Force, Satoru pilots the long-ranged combat Machina, Hind-Kind. He holds Moritsugu in high regard, and follows his orders without question. Possessing a very aggressive combat style, he considers Factors to be murderers, though he, himself, dislikes and avoids taking the lives of others.

In the manga he is introduced using the Japanese pronoun for 'he' which is, 'kare' appears in Hiragana next to the kanji for 'he' or 'him'; "そして彼が (Soshite kare ga) Yamashita Satoru-kun da." This can be found in the original Japanese manga, Volume 2, page 86. Additionally, "Satoru" is traditionally a masculine name in Japan.

While many fans based their assumptions about Yamashita's gender on outward appearance (i.e. being flat chested, his JUDA uniform, only one earlobe pierced, and his "masculine" body language) it is not uncommon to find gender-bending characters in Japanese anime, comedy or dramas - past and present.

Other gender questions have arisen from the original manga (Volume 0) when Shizuna presents Yamashita in a bikini. This causes Izuna freak out and exclaim that Shizuna's joke has gone too far Izuna further states that Yamashita should be embarassed to be dressed like a girl. During this same scene Hayase suffers from an explosive nosebleed (synonymous with sexual excitement) and passes out; which leads to Kizaki speculating about Hayase's sexual preference. This moment is also captured in episode 12 ("Tropic of Love") of the Linebarrel anime. While it is clear that Yamashita is a male, it is unclear about what sex he prefers.

The Wikipedia article (in the Manga/Anime ring) does refer to Yamashita as a girl. However; this mistake was based on an English scanlation of the manga that has proliferated on the Internet.