Diane (ダイアン Daian?) is a member of the Resistance movement at Outer Heaven. She was formerly a vocalist of a positive punk band, called Thin Wall, and uses her feminine charm for intelligence activities. Having gone on several intelligence missions in Outer Heaven, she has accumulated knowledge about the mercenaries and armaments of Outer Heaven. During Operation Intrude N313, she provided her expertise to Solid Snake, informing him of the weaknesses of each of Outer Heaven's mercenaries. She apparently had romantic feelings for Snake, but never expressed them to him. She lived with her brother Steve, who would often answer Snake's calls only to be annoyed with him and provide excuses for Diane's absence.
It is unknown whether Diane or Steve were still present in Outer Heaven during the NATO bombings after Operation Intrude N313, and if so, whether they survived or not.