[2] He went to Kyoto and taught in the dōjō of a man named Yoshida, who had relied on Saitō's father Yūsuke in the past.

[3] The same age as Okita Sōji and another member named Tōdō Heisuke, the three shared the distinction of being the youngest in Kondō Isami's group and being among its most gifted swordsmen.

At rest he always sat in the formal position, called seiza, and he would remain very alert so that he could react instantly to any situations that might occur.

In the reorganization of the ranks in November 1864, he was first assigned as the fourth unit's captain and would later receive an award from the shogunate for his part in the Kinmon incident.

His controversial reputation comes from accounts that he executed several corrupt members of the Shinsengumi; however, rumors vary as to his role in the deaths of Tani Sanjūrō in 1866 and Takeda Kanryūsai in 1867.

Later in late December 1867, Saitō and a group of six Shinsengumi members were assigned to protect Miura Kyūtarō, who was one of the major suspects of the assassination of Sakamoto Ryōma.

Saitō, along with the few remaining men of the Shinsengumi who went with him, fought against the imperial army at Nyorai-dō (a small temple near Aizuwakamatsu Castle), where they were severely outnumbered.

After Aizuwakamatsu Castle fell, Saitō and the five surviving members joined a group of former Aizu retainers who traveled southwest to the Takada Domain in Echigo Province, where they were held as prisoners of war.

[6] Saitō, under the new name Fujita Gorō (藤田 五郎), traveled to Tonami, the new domain of the Matsudaira clan of Aizu.

Fujita fought on the Meiji government's side during Saigō Takamori's Satsuma rebellion, as a member of the police forces sent to support the Imperial Japanese Army.

[11] During his lifetime, Fujita Gorō shared some of his Shinsengumi experiences with a select few, these included Aizu natives Yamakawa Kenjirō and Takamine Hideo, whose houses he frequented.

During his life in the Meiji period, Fujita was the only one who was authorized by the government to carry a katana despite the collapse of the Tokugawa rule.

Saitō's appearance in Nobuhiro Watsuki's Rurouni Kenshin series is likely the best-known of his manga and anime incarnations.

The series introduces Saitō as an anti-hero and eventual ally to the protagonist Himura Kenshin, and depicts several of the known historical descriptions of him from real life, from his personality and role in the Shinsengumi to his being left-handed.

His famous 'swift death to evil' (aku soku zan) motto in the series was also the theme of an entry in the 2000 International Obfuscated C Code Contest,[16] in which a series of programmed source code featuring his anime portrait in ASCII Art wrote other programs that eventually formed a loop spelling out aku soku zan.

Saitō is featured in the manga Getsumei Seiki, in later episodes of the anime Shura no Toki: Age of Chaos, and the video game series Bakumatsu Renka Shinsengumi and Code of the Samurai.

However, Saitō changes as a man through his interactions with Kanichiro Yoshimura (played by Kiichi Nakai) during the last years of the Shinsengumi.

Saitō Hajime is also shown in the Hakuōki Shinsengumi Kitan otome visual novel games, as well as its film, anime, and manga adaptations.

Here, like his historical inspiration, he is very reserved and analytical, using a left-handed sword technique and later joining Itō's splinter group at the order of Hijikata.

In the 2013 Taiga drama Yae no Sakura, he is played by Kenji Furuya of Dragon Ash, and Shugo Oshinari portrays him in one episode of the NHK historical documentary series Rekishi Hiwa Historia.

Saitō also appears in the mobile game Fate/Grand Order as a limited 4-Star Saber-class Servant which debuted during the GUDAGUDA Yamatai-koku 2020 event.