Saitō Hajime (斎藤 一 Saitō Hajime?) A former captain in the localist Shinsengumi, Saitō has had a long time rivalry with Himura Kenshin, a former manslayer for the Imperialist cause. As a result of his involvement in the Ikedaya Affair, he and his Shinsengumi comrades successfully prevented the burning of Kyoto by an extremist faction of the Ishin Shishi. Nevertheless, the pro-shogunate forces were ultimately defeated and he was forced to go into hiding.
Saito has no compassion or mercy for his enemies. He lives by the Shinsengumi code "Aku Soku Zan" (悪即斬 -literally "Slay Evil Immediately", but more poetically rendered as "Swift Death To Evil"). He is rather morbid and arrogant. Nevertheless, none of these character flaws prevent him from being a superb investigator and fighter. He believes in peace and order, even in the society created by his former enemies. Anyone he considers to be corrupt or despotic, he targets for elimination.
During the series, Saitō joins forces with Kenshin to fight against Shishio Makoto. However, throughout the Kyoto arc, he considers Kenshin to be more of an adversary rather than an ally. After acknowledging Kenshin's vow to never kill again, Saitō decides to put an end to their rivalry.
Saitō is an able observer and a quick analyst (he in fact works as a spy for the government.) In addition to being a skilled swordsman, he is revealed to possess immense physical strength when he pummels the Herculean Sagara Sanosuke in a hand-to-hand fistfight. He considers Sanosuke to be a dimwitted amateur with mild potential, due mostly to Sano's lack of insight.
He is also revealed to be married to a woman named Tokio, but she has never been seen. He remarks at one point early on that he has a fondness for soba, a simple noodle dish.
Saitō is highly recognizable by his narrow eyes, "spider-like" strands of hair in front of his forehead (he is also often said to resemble a wolf), his propensity for smoking and the katana (Japanese sword) which hangs from his left side.
Saitō mastered several techniques of the "Shinsengumi-Kenjutsu." The "Hirazuki" (left-handed stab) technique that Saitō's Gatotsu resembles is based on the real fighting style of the Shinsengumi. Although the Gatotsu is the only the technique that Saitō performs, he has been able to perform the same technique in different stances.
The First Stance (Ishiki) is the standard, shoulder-level ground attack. He prepares by dropping into a partial crouch, both knees bent, left arm drawn back and right extended forward; he grasps the kashira (endcap of the tsuka, or hilt) of his sword with his left hand and rests the tips of the fingers of his right hand (usually the thumb) on the blade near its tip. The Second Stance (Nishiki) is a downward-striking attack. The direction of the Nishiki thrust is narrower, as well. The Third Stance (Sanshiki) is an upward-striking attack. Prepared identically to the Ishiki, he uses it to intercept an opponent assaulting him from above, directing his blade into the air instead of immediately forward.
However, Saitō also possesses another stance Gatotsu Zero Stance (Zeroshiki). Zeroshiki is an attack performed at point-blank range using all his upper body strength. This stance, unlike the first three, requires no prior preparation or footwork. Saitō's sword techniques are considered quite deadly, as the Gatotsu has only a precious few blind spots to be exploited. Despite the apparent inflexibility of using one attack repeatedly, it has many useful applications. The motion of the Gatotsu can also be used even with his bare hands.
Besides his overwhelming ability with a sword, Saito is extremely well-versed in hand-to-hand combat. His fighting style most resembles Boxing as he possesses amazing footwork, defense, and tremendous speed and power. This is evident when he decided to fist-fight Sanosuke and beat him almost effortlessly whilst receiving no damage whatsoever from his attacks. It's then pointed out that he purposely dodged Sanosuke's bad shoulder in order to keep the fight fair. Besides his superior in-fighting skills, Saito is also extremely analytical in battle, much like Hiko Seijuro, and can exploit his opponent's weaknesses quite easily, such as Kenshin's reliance on his quick judgement, to which he replies by kicking him to the back rather than with the sword despite having taken his sword up.