Netsuki appears as a young man with short red hair and short horns on his head.
Netsuki was initially very prideful and arrogant, especially about his abilities. He grew more humble after seeing the great difference in strength between himself and Rou.
He never forgets a grudge, and will hold on to it until he's satisfied.
He joined Parabellum after being freed from the Kirika Empire's slave army.
After seeing that Parabellum was only led by an Ogre (Ogarou) he decided along with Fuuki and probably Genki to rebel and take the command. But they were easily beaten...
Rou decided to use his Demon Orb to make some experiments.
Rou teached him Muay-thaï.
At Purgatory, during a friendly competition with adventurers (with Rou charging admission fees), 1,000 gold were offered as reward to anyone that could defeat him.
In the manga, adventurers could challenged him by paying a Silver Coin and could gain 5 Silver Plates by winning. If he had lost, he would have his training course doubled. He won all his fights.
It is later known that the Wolf Hero was the one who turned him into a slave.
He takes his revenge during the Holy War by killing him and kept his sacred treasure as proof.
Netsuki is skilled in the use of a sword and can emit flames under his control.
His Demon Orb Liberation manifests a double-edged one-handed sword.
He received a new ability ever since Ranking Up, called 【Purgatory Demon Sword】. His Demon Orb, that becomes a flamberge gushing flames when released, now becomes gigantic when 【Purgatory Demon Sword】 is used, and he enters a state where the flames he is clad in are strengthened. Because he becomes just like a miniature sun in such a condition, if one doesn't have 【Tolerance】 or 【Complete Tolerance】, it seems like it would be difficult to approach first.