Leader of the Guardian CourtThe fact that the BSSM series revolves around the life of Tsukino Usagi/Sailor Moon has made many fans believe that Sailor Moon is the leader of the Sailor Soldiers. In some ways this is correct as Sailor Moon is the Moon Princess and the heir to the Silver Millennium, making her the figure that all nine Sailor Soldiers pledge their loyalties to. However, this does not make her the leader of the Sailor Soldiers, but rather makes her their ruler. It must not be forgotten that the Sailor Soldiers' real duty is to protect and serve the Moon Princess. The Moon Princess was not a warrior in the past and was also never meant to be a warrior in the present. In the manga, Luna admits that she had only trained Usagi as a Sailor Soldier in order to protect and hide Usagi from the enemy. This is why when Usagi finally remembers that she is the Moon Princess that Venus is able to take her place as the leader:
Sailor Moon? No. Princess Serenity, you remember everything now, right? Do you remember me? About me, Sailor Venus? You know that I am the leader of the four soldiers that protect the Princess?1
Sailor Venus is the de jure leader of the guardian soldiers that protects the Moon Princess. Aino Minako was awakened as a Sailor Soldier when she was 13 and is therefore the first to accept her duty as a Sailor Soldier. She knew of her mission to protect and find the Moon Princess much earlier than the others and this is the reason for Venus's decision to disguise herself as the Moon Princess. Venus needed to protect Usagi's true identity till she was ready to step into her role as Princess. Also before joining the team, Venus also watches and trains the newly awakened Guardian team (Mars, Mercury, and Jupiter) via the Sailor V game. As further proof of her status, in the manga, Venus owns a sword said to be made of the same substance as the Imperium Crystal. Queen Serenity introduces the sword as the lengendary sword that protects the Moon Princess and bequeaths it to the Mars, Mercury, Jupiter and Venus. However, in the end, Venus is the only one who is able to wield and unlock the sword's true power. This sword later belongs exclusively to Venus and becomes part of Venus's repertoire of attacks. Takeuchi Naoko often draws Venus holding the sword in artbooks and promotional material and presents the sword as the symbol of her status as the Leader of the Guardian court. Venus's role as leader is clearly portrayed in the manga as Venus often takes the lead or makes the final decision in missions, strategy sessions, and important battles throughout the series. In the classic anime, her role as the leader of the Guardian court is not as clear. However, some references to her status as leader do exist. One such example is in episode 102, when Venus disguises herself as Sailor Moon in order to protect Usagi's identity from Kaolinite. Luna assigns Venus this task saying that as the Leader of the Guardian court, she must take on this mission and protect Sailor Moon at all cost. Interestingly enough, Venus is the only one in the Sailor Team (besides Sailor Moon) who has the ability to disguise herself. In the manga, she has her own transformation compact while in the classic anime series, she had to borrow Usagi's transformation compact in order to diguise herself.
the balancing factor, the "all-rounder"As most fans of the series have already noticed, Sailor Venus's fighting style is not offensive like Mars's and Jupiter's nor is it strategic/defensive like Mercury's. Therefore her role on the battlefield remains debatable among audiences of the manga and both anime series. The reason for such ambiguity is the difficulty in portraying her as the team's strongest balancing factor. In notes by the author and as seen in her years as Sailor V, Venus is a Sailor Soldier that is able to fight solo without any support and is therefore supposed to be the team's "balancing force."2 In the anime, the difficulty of portraying such a role has resulted in Venus's battle scenes being de-prioritized in favor for Mars's and Jupiter's preemptive strikes, Mercury's strategic analyses and Moon's finishing blows. When she is featured, she is often seen playing the diversionary role or secondary offense. In the manga, her fighting style and role as commander is more clearly portrayed throughout the series. Venus is seen directing and taking the lead in several final offensives against the series' various main anatagonists, reconnaissance missions, and covert operations such as infiltration into Mugen Academy. Venus also has more scenes where she fights enemies alone, allowing readers a glimpse of her true fighting style - a soldier that is well-balanced offensively and defensively and capable of fighting solo.
2. Information courtesy of Japanese wikipedia on Aino Minako.