Marmaduke Brown is a member of the Hachiō Executioner Blade.
Marmaduke's appearance is that of an overall medieval knight. She wears a large dark armor with a spiked helmet with two spikes on the sides and one in the back. Her overall gear has a cape and a shield on her left arm and a long one-bladed axe and a short sword which she keeps strapped to the lower back of her armor and the whole armor itself grants her a large bulky appearance, which leads most people to believe that she is a man. It was later revealed by Kensei Ma that she is in fact a woman, as was shown after he rips the armor off of her, revealing her feminine body underneath.
Despite the large masculine body armor that she wears, underneath that armor Marmaduke has quite the feminine body, as was shown after having her armor removed by Kensei Ma. She is a tall woman with a very curvaceous figure, with well-endowed breasts wearing an revealing short medieval-styled top with straps down the middle and a pair of underwear that matches the medieval style of her top. It is currently unknown what her face/head looks like on account of the fact that she stills has her helmet, but the staff at Wazadepa stated that she is a beauty.
Based on Raki's facial reaction and surprise, it seems like even the Hachiō Excecutioner Blade members had no idea that Marmaduke was a female while based on Mihai's and Rin's reaction/comment, they were well aware of who Senzui was.
- Master Axewoman: As a member of the Hachiō Executioner Blade, Marmaduke is a highly-skilled master of weapons that specializes in the use of long Axes, making her a Master Axewoman. Her skill in using the axe is great enough for her to destroy a multitude of battle turrets in a matter of minutes while simultaneously manhandling the whole convoy and destroying their guns. She is so skilled in using her axe, that she was able to perform the Shinto Gōrenzan technique using only her axe instead of an actual sword.
- Master Knight: Marmaduke is a grand master trained in the history and style of being a knight. As a result, she is trained in the way of the knights and trained in traditional swordplay and shield fighting. She is very skilled with her shield as she was able to block multiple attacks from various grand master leveled fighters including Kensei Ma. She is also able to use her shield as a makeshift weapon as shown during her attack on the convoy. Despite specializing in the use of axes, she is trained in swordplay, and is a good enough master to be able to perform Shinto Gōrenzan, which is known as the highest level of sword mastery.
- Immense Speed: Despite wearing a large suit of armor, Marmaduke is shown to be extremely fast. She was fast enough to be able to run on water and was fast enough to continuously outpace and blindside Kensei Ma during all of his advances on Raki Hoshinano, despite Kensei being a master known for his speed and being at his fastest when harassing women. What made her feat of running on water more impressive than the other masters (Hayato Furinji, Mikumo Kushinada, and Seitarō Raigō) who have shown this ability is that Marmaduke was able to do so while donning heavy knight armor and wielding heavy metal weapons while the other three masters had done so while wearing light clothing.
- Immense Strength: Marmaduke has shown herself to be incredibly strong as she was able to single-handedly destroy an entire convoy by herself. She was also shown enough strength to run towards the convoy ship without being hindered by the turret firing at her nor the strain of the heavy armor she was wearing at the time.
She was first seen running on the water to one of the battleships surrounding her fellow weapons members. She easily blocks the bullets firing at her and gets on the ship and easily destroys the turrets and guns the soldiers are using.
When Miu and Kenichi try to run away, the knight blocks their path. Once Shigure used her Soutou Kyourenzan, she is forced to fight her 'shadow' while allowing Miu and Kenichi to escape with Mycroft and Christopher.
Later, she is seen partnered with a Mikumo Kushinada in another country fighting soldiers beginning the Eternal Sunset. Afterwards Marmaduke, along side Mikumo, Sōgetsu, Mildred, Edeltraft, Raki, Ştirbey, Hongō, Agaard, Cyril, Rin, and Ogata all faced off later against the masters and allies of Ryōzanpaku. When the Ryōzanpaku masters begin to go on the offense, Marmaduke engages battle with them. When Kensei attempts to attack Raki (in a perverted manner), Marmaduke protects her by crashing Kensei with her shield and engages battle with Kensei.After some of the Yami masters have a change of heart, they are attacked by Sōgetsu, Cyril and Agaard. Assisted by Cyril's mantra, the Ryōzanpaku masters (along with Sōgetsu and Agaard) stage a counterattack against Yami. Edeltraft and Marmaduke are damaged from the counterattack as Ma Kensei suddenly senses the swaying of breasts. Marmaduke tries to fight off Kensei but he manages to reach and remove Marmaduke's armor, revealing her to be a woman.
Cyril then uses his mantra on Marmaduke and Rin, who are forced to defend, while Sougetsu runs past Rin and attacks Marmaduke.
Once Yami loses the battle, Marmaduke retreats with everyone else in complete defeat.