Katana is a follower of Bushido, which can be translated as "the Way of the Warrior." Bushido was the philosophical, spiritual and ethical system followed by traditional Japanese samurai as well as many non-warriors from in earlier periods in Japanese history.
Today Bushido remains a strong influence in Japanese society, but it is rarely regarded as a "religion" in the same sense that popular Japanese religions Buddhism and Shinto are. For most Japanese people, Bushido can certainly not be said to be their "religion." Katana is a rare individual, however, in the degree to which she has adopted the Samurai lifestyle and belief system. Katana consciously follows Bushido teachings that even most contemporary Japanese citizens find archaic or unnecessary. Katana trained as a Samurai under the master Tadashi, and that tutelege may be the principle source of Katana's allegiance to Bushido. Katana's identity and "power" as a superheroine is strongly tied to her mystical sword, which is named Soultaker. Katana's sword was forged and imbued with power in the 14th Century, during the height of Samurai/Bushido culture and influence in Japan.
In addition to her identity as a Samurai and her adherence to Bushido, it would not be surprising if Katana considers herself a Buddhist, which is what most Japanese people name as their religious preference. Many Japanese people call themselves "Buddhists" out of habit or tradition, even if they are not active Buddhist worshippers or conscientious followers of Buddhist teachings. We are unaware of whether Katana has identified herself as a "Buddhist." Nor are we aware of any instance in which Katana has identified herself as a Shintoist. Regardless of what Katana might specify if asked about her religious preference, Bushido is demonstrably her principle philosophical system.
From: "Katana (comics)" page on Wikipedia.org website (http://en.wikipedia.org/wiki/Katana_(comics); viewed 8 June 2007):
Katana is a DC Comics... a superhero. She first appeared in the The Brave and the Bold #200, and became a longterm member of the Outsiders.
Tatsu Yamashiro was an average Japanese girl, save for her proficiency in the martial arts. Two brothers, Maseo and Takeo Yamashiro, both proclaimed their love for her. While she liked both, she chose Maseo. This angered Takeo, who refused to attend the couple's wedding. By this time, he had joined the Yakuza, receiving a large dragon tattoo across his chest to mark himself as such. As a result, his family disowned him.
After the deaths of Tatsu's parents, ...she and Maseo started a family of their own, and she gave birth to twins, Yuki and Reiko. Meanwhile, Takeo rose in rank of the Yakuza, and one of his exotic tastes included ancient weapons. He was presented with a pair of matched swords by General Karnz, one of which Takeo favored due to its mystical properties, which would come to be known as the Soultaker.
One night, Takeo took both swords to the Yamashiro residence. Tossing the non-powered sword to his brother and demanding he duel for Tatsu, he quickly struck Maseo down. In the course of the fight, Takeo accidentally started a fire, and while distracted by his children, Maseo was slain with the Soultaker.
Tatsu arose just in time to see her husband die, and engaged Takeo, gaining the upper hand and disarming him. When she attempted to go after her children, she heard her husband's voice telling her to turn back - coming from the sword. She listened, and watched as her house burned.
Tatsu began training as a samurai under a master called Tadashi. After much time she graduated from his tutorship and left for America where she intended to use her talents to fight for justice. She took the codename Katana after the sword that she wielded...
[Katana joined Batman's newly formed team the "Outsiders" and moved to Gotham City.]
...Takeo was still at large and had followed Tatsu to Gotham City. Secretly he switched swords with her and left for Tokyo with the Outsiders on his tail. Takeo took the sword to his master, the godfather of the Yakuza, known only as the Oyabun. Performing a specific ritual, the Oyabun and Takeo managed to recall the souls that inhabitated the sword, who proceeded to take corporeal form. Among them were legendary mercenaries and assassins, but also Maseo, who was now a slave to the Oyabun. Katana had to fight them all and after a long battle that took its toll, Katana was able to reclaim the Soultaker and kill Takeo, and she could finally put an end to some of her ghosts. By undoing the ritual however, her husband returned into the sword as well.
...After a while, the team disbanded... Nonetheless the Outsiders were forced to defend Markovia against the Manhunters, but during the fight [Katana's teammate] Halo was knocked into a coma, saving Katana's life. Bounded by giri-ninjo (a debt of honor even unto death), Tatsu left the team so she could tend to Halo's wounds. During that time however, she was approached by a family member of her husband, who wished her to accompany the Suicide Squad on a mission to destroy a large horde of weapons that was about to be sold to the Yakuza. She declined on the basis of her giri-ninjo, although she was willing to help if the need was truly desperate.
That family member was later killed, and she went after the killer, the Daichi-Doku's Oyabun (of which her relative was a member), who did not wish to see the weapons destroyed and tried to stop the Suicide Squad. During that adventure, she saved the life of Bronze Tiger and Manhunter (Mark Shaw), making them honor-bound to her by giri-ninjo. Mark Shaw then assisted her in taking down the Daichi-Doku's Oyabun. The Oyabun commited ritual suicide and Katana stood by as his 'second', ready to help with a blade strike so he could keep his honor.
...During a lone mission, Tadashi, her old mentor sent Lady Shiva to claim Katana's Soultaker sword. Shiva confronted Katana who had been battling a gang of drug dealers. Katana had slain many, but refused to kill the youngest member, something Shiva insulted her for. Shiva being world-renowned as the world's greatest assassin and fighter, was able to kill Katana. Katana returned back to life after a trial by combat within her sword, which included confronting many of the souls of the people she had killed. Afterwards, she manages to find her old mentor and take his life...
The Soultaker, along with its non-powered twin, was forged in the 14th century by Muramasa, whose swords were said to be cursed and make those who were evil commit evil acts. It sometimes takes the souls of those it kills, storing them inside the sword, where they can engage in limited communication with whoever wields it. These souls can be reincarnated by the means of a sacred ritual, under which they serve their summoner, even if it is against their will.
From "He's strong! He's powerful! He's fantastic! And he prays!" forum discussion page started 1 October 2002 on ToonZone.net website (http://forums.toonzone.net/archive/index.php/t-50423.html; viewed 12 July 2007):
10-04-2002, 09:35 AM
Hey let's not forget the Green Arrow, Connor Hawke, the Tibetian Buddhist.
Hmm... Are there any other Buddhist Super-Heroes?
10-04-2002, 01:16 PM
Well, you could probably make a case for Katana of the Outsiders being a Zen Buddhist as part of her samurai training, but the connection is tenuous at best. You could make the same case for any of the "martial-arts" heroes (like Shang-Chi). Maybe Bulletproof Monk, though I've never read that comic...
From: "Religion in Comics" forum discussion, started 17 May 2007 on official DC Comics message board website (http://dcboards.warnerbros.com/web/thread.jspa?messageID=2003785241; viewed 7 June 2007):
Posted: May 17, 2007 8:37 AM
Yesterday, I read Action Comics #849, and the issue had several religious references and implications. Because of this, I decided to discuss it with everyone else here. Does religion have a place in comic books?
Posted: May 17, 2007 9:43 AM
Actually religion can do a lot to inform you of a character's backstory.
What if you found out your fave was into Scientology? Zen? or maybe as a Moslem? Christian Scientist.
...Obviously Wonder Woman believe in the ancient gods or the Greek pagans.
And Lobo's conversion to the Church of the Threefold Fish really made that arc work a lot better than if maybe he was being mind controlled.
Katana - gotta be Shinto...
Plus we have a universe with an entire planet that worships Darksied.