Sentomaru

Sentoumaru is the captain of the Marines' Science Unit and bodyguard of Vegapunk.

Marines
Sentourmaru refers to Kizaru as "Uncle" (Kizaru-jii-san, a Japanese honorific), although the Japanese term used does not mean they are family, but rather the pair are on a high level of respect (despite Sentoumaru shouting at Kizaru for using the wrong Den Den Mushi).

Pirates
Sentoumaru claims that he doesn't "particularly have anything against pirates", but nevertheless fights against the Straw Hats with PX-1 and Kizaru, and is anxious for Kizaru to contact him, fearing that if he does not, none of the pirates will be left for him to deal with.

Powers and Abilities
Sentoumaru is seen carrying a massive broadaxe, but has yet to use it in battle.

As Dr. Vegapunk's bodyguard, he claims to have a world-class guard. He fights similar to Bartholomew Kuma's style, standing like a sumo-wrestler and striking with open-palm strikes, which are strong enough to push back and injure Luffy. Sentoumaru's first named attack is Ashigara Dokkoi, where he smashes his opponents with an open-palm with extreme force. He is also seen jumping a far distance to pursue an escaping Luffy.

Despite all this, he claims he is not a Devil Fruit user.

Sabaody Archipelago Arc
Sentoumaru was first seen on top of a building when Dias attempted to escape his slavery from his Tenryuubito enslavers, although not introduced then. Sentoumaru had been disappointed that Dias could not possibly have survived in the New World.

When Kizaru arrives on the island he attempts to look for his subordinate but is unsuccessful. Later Sentourmaru is seen on top of a building wondering why Kizaru had not conatcted him, since the fight had already started. When Sentoumaru finally contacted Kizaru, Kizaru was scolded by Sentoumaru for trying to use a Black Den Den Mushi instead of his Baby Den Den Mushi.

After the Straw Hats defeat PX-4, Sentomaru arrives, revealing only his name in passing, and attacks the Straw Hats with PX-1. Luffy attempts to split up the Straw Hats, but Sentomaru goes after him, Robin and Chopper; PX-1 pursues Nami, Franky and Sanji; and Kizaru intercepts Zoro, Brook and Usopp. Sentomaru knocks Luffy back with his attacks, claiming to have the strongest defense in the world.

Trivia

 * Sentoumaru's name contains the kanji for "peach" in reference to the Japanese story Momotaro, from which the admiral names are also derived. His design is also similar to that of the Japanese folklore hero Kintarō (also known as samurai Sakata no Kintoki), who was notable for carrying a massive axe and his raising wrestling bears. (possibly showing his close connection to the Kuma-clone Pacifista)