Captain Maeko Matsuo is the human head of the ERCS security forces at Port Hanshan, on Noveria. She is one of the officers who confronts Commander Shepard upon the SSV Normandy's arrival. Matsuo's name and frequent use of Japanese honorifics hint that she is of Japanese ancestry.
Unlike Kaira Stirling, Matsuo is quite level-headed and accommodating, but stands firm when asking Shepard to disarm and only stands down when Gianna Parasini confirms the Commander's Spectre status. Matsuo seems to be one of the few uncorrupted officials at Port Hanshan; Lorik Qui'in says she has no idea some of her officers are being bribed by Administrator Anoleis.
Shepard can talk to Matsuo after Parasini has welcomed the squad. When asked why Matsuo is still standing in the docking bay as if she is guarding the Normandy, Matsuo tells the Commander she is protecting the local corporations "from themselves", preventing them from doing anything stupid to a Spectre's vessel. If Shepard asks her about her background, Matsuo jokes "You first", and asks why the Commander became the first human Spectre.
Matsuo says she is an ex-marine who served for ten years: she came under fire several times, which is how she gained her position on Noveria. Most of her job is diplomatic, keeping all the corporations in line. Sometimes it takes Matsuo's security forces to ease hostile negotiations between companies. Shepard can be honest or dismissive about the ERCS deaths at Synthetic Insights. Either way, Matsuo takes the news quite well, as she has warned her subordinates about the consequences of taking jobs "on the side". She is not surprised Stirling was involved, describing her as being quite mercenary, and asks Shepard to leave so she can write letters to the victim's families and make the funeral arrangements.
If Anoleis and Parasini kill each other due to events regarding the former's financial crime and Shepard tries to take Anoleis' garage pass from his body, Matsuo arrives at the scene with an ERCS corporal, ordering him to seal the area off and asking Shepard about what happened.
If Shepard divulges the circumstances around it, Matsuo concludes that Anoleis was always paranoid and prone to panic. If Shepard feigns ignorance, Matsuo questions the Spectre further but ultimately drops the matter when she forms her conclusions. Matsuo apologizes for presuming to remind Shepard what the Spectre's job is if Shepard flippantly disavows jurisdiction over common criminals.
Whatever the case, Matsuo excuses herself with the claim that records on executive deaths must be filed in triplicate.
When Shepard and the squad fight off the geth that Matriarch Benezia left to guard the garage, Matsuo rushes her guards to the garage and demands to know what is going on; after Shepard's explanation, she replies that she cannot believe that there are geth on Noveria. Matsuo tells Shepard that if the geth were packed in Benezia's cargo, there could be dozens of them and warns the Commander to be careful. The captain then leaves, saying that if word gets out about the geth, there might be an investor panic.
- Maeko's references to Gianna Parasini as "Parasini-san" and Matriarch Benezia as "Benezia-sama" are typical examples of polite language in Japanese. The "-san" qualifier is usually employed when politely referring to someone of relatively equal social standing, and the "-sama" qualifier is used in very special circumstances when referring to someone of much higher social standing, usually outside of one's social "in-group". Her way of referring to Kaira Stirling, who is her subordinate among the Noveria port security personnel, as "Stirling-san", however, is slightly at odds with modern Japanese conventions of politeness.
- Maeko Matsuo's voice actress, Kim Mai Guest, also provides the voice for Hana Murakami in Mass Effect as well as Dawn Star in Jade Empire.