Sirius is a fairly tall and muscular young man who has a small amount of piercings all over his body. He has bright red eyes and long, spiky black hair that hangs down the back of his head, leaving his forehead mostly exposed. His standard attire consists of a black tunic with a dark gray belt wrapped around his waist, and similarly colored lines running up the portion covering his chest. Around his neck he wears a long black scarf, as well as a hanging collection of what appear to be feathers hanging over his shoulder. He also wears dark-brownish-red studded gloves.
On his lower half he wears dark tan pants with large black boots with silver trimmings on his feet. Oddly, he seems to have no visible eyebrows, with those apparently replaced by a series of piercings.
When first introduced, Sirius appears as a highly competitive individual, and is almost cruel in his desire and ways of insuring victory, even purposefully crippling potential opponents before the start of the Hunter Examination. However, he also seems highly confident in his own fighting skills, declaring that he could easily defeat most of the contestants anyway, and even going so far as to refuse to use his actual Hatsu when fighting Knave during the Examination (though Knave himself also refused to show his).
However, following his defeat at Knave's hands, Sirius seems to have accepted some humility and mellowed considerably, greeting Knave and his companions as old friends the next time they meet. However, he still has a healthy rivalry with Knave, and the two constantly argue and brawl in order to discover who is stronger (though this is usually used for comedic effect, via a dust cloud or the like). He does, however, respect him a bit more, and is more likely to team up with Knave against an opponent neither can defeat alone.
When it comes to combat, Sirius appears to be a ferocious and merciless fighter, willingly attacking an opponent's limbs with the intention to break them, and thus, cripple the opponent, leaving them unable to fight. He also seems highly arrogant in his abilities. However, he has slowly began becoming more honorable in the ways of combat, though he will still resort to slightly underhanded tactics if pushed far enough.
While it is currently not known how Sirius learned how to utilize Nen, he has been shown to be a Transmuter, with his ability being titled Mako.
Ko (硬, Temper) is an enhanced version of Gyo in which all of an individual's aura is concentrated into one particular body part. Zetsu is used to completely stop the flow of Nen in all other parts of the body. This makes that one body part exceptionally powerful, but leaves the rest of the body completely unprotected. This was Sirius's most common offensive Nen technique during the Hunter Examination.
Ken (堅, Fortify) is the advanced version of the basic Ren technique. Ken is a defensive technique where a Nen-user maintains a state of Ren over their entire body, allowing them to defend against attacks from any direction without the need to use Gyo. Ken is as useful as a defensive position, but is tiring to maintain. Additionally, it is not as strong as Gyo on any given part of the body, since it protects the whole body evenly. Because of that, it is used to guard when one wants to be cautious. This was Sirius's main defensive technique during the Hunter Examination.
Superhuman Strength- Sirius has a generally larger pool of strength than a normal human being, with him able to break bones and sufficiently injure opponents with just his bare hands, and is even able to catch one of Knave's punches with one hand and seems initially unfazed by it.
Superhuman Durability- Along with his strength, Sirius has a great amount of durability, even without his Hatsu, able to take truly incredible hits and be able to stand up after it. Even when hit by attacks that would kill a normal person, Sirius has been shown to be able to force himself back up afterwards, or at the very most is knocked out or at worst, is near death.
- Sirius's appearance, and roughly his abilities as well, are based on the character of Gajeel Redfox from the anime/manga series Fairy Tail.