Danjo's heir and strongest member of the Kouga ninja. He's a peace-loving idealist who's genuinally in love with Oboro and wants to put an end to years of hate and rivalry. His special power is a "Do Jutsu" (Fierce Ability) in his eyes, that allows him to send an attacker's killing intent back at him. Commits suicide after witnessing Oboro's suicide.
A fat, jolly ninja who's often seen near Gennosuke. Despite looking like a moron, he's very competent and quite smarter than he looks. His body is like a rubber balloon, making him able to squeeze through small openings. Is killed by Jingoro, who forces himself down his gullet while in snail form.
One of the more mysterious and grotesque members, he's said to be an astromancer ad a seer. He has no arm nor legs, but can fight with an extremely long tongue and a knife hidden in his throat. His scale armor allows him to crawl around really fast like a snake. He's bifurcated by Tenzen.
In the Novel, He's "just" quadriplegic, but can still regurgitate blades at high speed and turn his skin in a scaly, hard hide.
Knife Nut: Hidden down his esophagus, though it is called a "spear" in universe.
Meaningful Name: Jimushi means "Earth Insect". Look at him when he crawls on the ground, moving like a centipede.
Oh Crap: Sadly he didn't know about Tenzen's resurrecting skills.
Overly-Long Tongue: His only weapon. Though considering how freaking skilled he is in using it to replace his limbs.
Member of the Kouga Ninja he's a short and sneaky guy whose eyes are always shut. He's Okoi's older brother. His powers allow him to transform into anyone, simulate voices and even change his size. He's eventually tricked by Tenzen and killed by the soldiers escorting the Iga ninja.
Beware the Nice Ones: Despite his docile looks, this is the same dude who slices Hotarubi's arms off and then proceeds to impale her against a tree.
Big Brother Instinct: Towards Okoi. When she died, all bets were off in regards to him. Certainly explains the horrible way in which he killed Hotarubi, when not even a single hour had passed.
Manipulative Bastard: Can be very sly and sneaky. Especially seen when he imitates Akeginu's voice to confuse Koshirou and allow Kagerou to give him a Kiss of Death.
Master of Disguise: He can turn into anyone at will by taking a model of their face from a mud mask. It's stated that he can even change his height, but for some reasons he can't copy the nostril's hair.
The anime noticeably made him less ruthless and more sympathetic.
Oh Crap: When Oboro's eyes disband his perfect disguise as Yashamaru and much later, (while disguised as Tenzen) when the soldiers (and Tenzen among them) reveal that Tenzen's powers involve coming back from the dead.
Pet the Dog: Briefly turns into Yashamaru to comfort Hotarubi as she's dying.
A good friend of Saemon and Danjo's advisor. He's Gennosuke's maternal uncle and he taught him everything he knows, including the Dojutsu. He appears to be blind and has an excellent hearing but he can actually use the dojutsu, but only by night. Gets killed by Koshirou, since being blind he's able to work around the Doujutsu's only weakness.
Died Standing Up: Against Koshirou, driving him mad as he can't determine if his opponent is dead or not.
Handicapped Badass: The man has severe eyesight problems, though the exact source and effects vary per media. In any case, he's still not to be trifled with.
Parental Substitute: Helped raise Gennosuke after the death of his older sister aka Gennosuke's mom.
A large and massive ninja of Kouga. Always seen around Hyouma and Saemon. He's very strong and can merge with the groud and any solid surface, allowing him to move around unseen. As a child he was traumatized by his father's death and shaved his head because of that. He's impaled by Tenzen while trying to flee from him and his corpse is merged inside a wooden panel, exhibited as a warning to the Kougas.
Leeroy Jenkins: At one point he decides to leave the main group despite Gennosuke's plans and directly go for the Iga ninja.
He might have pulled it off, too, if not for Tenzen's resurrection powers, and the accidental death of an innocent father.
My God, What Have I Done?: In the anime, he's horrified when he mistakenly kills the flautist father in front of everyone, including his kid. The fact that his dad's death was his own Start of Darkness doesn't help. And it gets worse as his shock over that is what lets Tenzen kill him.
Odd Friendship: In the anime he gets along pretty well with Okoi, and they're even shown hunting boars together.
One of the two kunoichi of Kouga, she's Saemon's little sister. She's a large, well muscled girl who a tomboy, but she's ready to take advantage of her large breasts if needed. She's a human-leech who can drain people's blood from her skin, causing also physical pain. She gets captured and tortured by the Iga clan and eventually is killed by Nenki while trying to escape.
The other kunoichi of the Kouga clan. She's a feminine woman with black hair and red lips, madly in love with Gennosuke and vehemently jealous of Oboro. When she's aroused, her breath becomes a poisonous miasma. She's horrifically raped and tortured with needles by Tenzen, which drives her into insanity.
Angst: Given her powers, this is pretty justified.
The old leader of the Iga clan, she used to be in love with Danjou. Her powers are unknown but she seems to have a tamed falcon as a pet. She's the very first person to die in the manga, killed by Danjou's needles. Though not before she takes him with her.
Brutal Honesty: When informing Oboro that she's far too clumsy to be a ninja. (Though she's not as harsh in the anime.)
Ogen's granddaughter and Gennosuke's soon-to-be wife. She's a very sweet and clumsy person. She can't fight, but her eyes have the power of cancelling any ninja power or technique seen, which is considered as one of the most deadly powers in the whole series. After going through a long series of Break the Cutie moments she kills herself in order to allow Gennosuke to win.
Spanner in the Works: Thrice, actually. First she seals her own Anti-Magic eyes with the Seven Days Ointment so she won't be tempted to use them against her own clansmen — also making impossible for Tenzen to use her against others. Later, she's vital into killing Tenzen himself when her eyes are unsealed right when he's reviving himself. And last but not least, her death derails Ofuku's own gambits, sending her into a mighty Villainous Breakdown.
Nice Guy: He's one of the few ninjas who doesn't really enjoy fighting and prefers to live peacefully with Hotarubi.
Razor Floss: Made from the hair of deceased women bathed in a special oil. In the novel, it was a single rope.
Traumatic Haircut: During the battle against Shogen, his long black hair gets hacked off by his own weapon.
A very high-ranked Iga ninja serving Ogen, he's one of the strongest members, and surely one of the most evil characters in the manga, and that's saying something. He's the mastermind behind the Iga-Kouga war. Has an unhealthy attraction for Oboro. Thanks to a parasitic twin living in his body he can come Back from the Dead at will. Is eventually beheaded by Gennosuke and destroyed when Oboro use her Anti-Magic on the parasite twin while at work, thus nullifying his powers.
Adaptation Expansion: In the manga, his parasite is identified as his younger twin brother, while in the anime the parasite is the ghost of Tenzen's mother, killed long ago by his father, and now manipulating his son for revenge.
Back from the Dead: He was born with a parasitic twin inside his body. Said twin is normally seen as a small bulge on his ear. If Tenzen's killed, the twin reach the wound and "eat it", allowing Tenzen to raise from the dead.
Big Bad: Surely he's the most suitable character for the job.
Body Horror: How his resurrection works. This gets disgustingly bad the last time, when you see the parasite using Tenzen's sliced neck as a mouth to speak.
Who Wants to Live Forever?: Many people would consider immortality quite awesome, though in the anime he affirms that he has lived for so long and has been resurrected so many times that for him, immortality is the worst of curses.
An old shinobi who can stretch his limbs and neck like boneless tentacles. He's grumpy and easy to anger. Meets his doom in Okoi's arms.
Animal Motifs: His elongated skull and his tentacle-like limbs can make you think of a squid.
Badass Grandpa: Shown to be strong enough to smash a stone wall to pieces with a kick.
An odd-looking shinobi with very long and messy hair, huge eyebrows and long nose hairs. He can animate and control all the hairs of his body and can use a long staff. Hyouma use his dojutsu on him, causing him to break all his own bones.
A skilled warrior and shinobi, he's very protective towards Oboro and possibly in love with her. He obeys the orders of Tenzen, his Evil Mentor, but he's not as evil as him. Can fight with two kama sickles and use his breath to form a deadly Razor Wind attack. Halfway through the manga he's blinded by Gennosuke, who sends back his wind at him, but learns how to fight while blind. He's eventually poisoned to death by Kagerou, whom he thought was Akeginu thanks to Saemon mimicking her voice to distract him.
Disability Superpower: After being blinded he gains a better sense of hearing, allowing him to fight and kill Hyouma as now he's immune to his gaze.
Dual Wielding: Sickles. He can even throw them with deadly precision.
Even Evil Has Standards: He's clearly not okay with the idea of Tenzen forcing himself on a defenseless Oboro. In fact, as this happens, Koshirou is outside the room and clearly forcing himself to not intervene, torn between his loyalty to the one who raised him and his own love for his lady-of-liege.
A slug man from Iga who can melt his body with salt in order to lay ambushes and move faster. However too much salt reduce him to a pitiful squealing worm. Water can return him to normal. He's deeply afraid of the ocean for obvious reasons. He's killed by Gyoubu who tosses him in the sea, causing him to melt before Akeginu can help him.
Why Did It Have to Be Snakes?: He's scared shitless of the sea. Justified as, due to the salt in it, his body would melt upon prolonged contact. And that's what happens to him.
Iga kunoichi, she's a beautiful woman who serves as Oboro's maid and actually cares for her plea. She can expel blood from her skin and use it in battle along with daggers and shortswords. She's in love with Koshirou. She's eventually tricked and captured by Saemon, and stabbed in the heart by Kagerou.
Mundane Utility: In the novel, she uses her blood powers to cover herself with "clothes", so Jousuke wouldn't know he had won a bet between them involving her becoming his wife for the night if he could remove her top.
Kunoichi from the Iga clan and Yashamaru's lover. She can summon and control insects and snakes to do her bidding. She's only sweet and gentle with Yashamaru, and tends to be violent and rude to anyone else. She's maimed and killed in battle by Saemon.
Death Glare: Her default expression around anyone who's not Yashamaru. Though even he gets one when he jokes about Oboro's cuteness. It's really funny.
Friend to All Living Things: She can use her powers to summon butterflies against her enemies, though she also has a pet snake and in the manga she can control many kinds of bugs. In the novel, is stated that she can use her powers on both insects and reptiles.
Tokugawa Ieyasu: The elderly former Shogun, who appears to be suffering from some sort of throat cancer as evidenced by the bulbous growth beneath his chin. Although retired, he still possesses enough influence within the government to revoke the Hattori truce in order to resolve the succession dispute. Historically, Ieyasu is regarded as an effective but extremely heartless ruler: Basilisk maintains this image of him as he clearly views both Koga and Iga as expendable in the face of ensuring political stability and his family's grip on power, thus forcing them to fight to the death.
Hattori Hanzou the First (Masanari): The head of a prominent ninja family from Iga Province who would later become chief of the Shogun's intelligence. In the anime, he helped the people of Tsubagakure escape Nobunaga's attack. The peace treaty between Iga Tsubagakure and Kouga Manjidani was originally implemented by him.
Hattori Hanzou the Fourth (Masahiro): The third son of Hattori Hanzo and the current leader of the Shogun's intelligence. Although he dislikes the idea of turning Koga and Iga loose, his loyalty to Ieyasu compels him to nullify his father's anti-war pact for the sake of avoiding civil war among the other Shogunate retainers. He was among the audience that witnessed the duel between Yashamaru and Shogen at Sunpu Castle and would later witness the duel between Oboro and Gennosuke alongside his adopted son Kyohachiro and Lady Ofuku. Although his demeanor can be considered cold and non-chalant, he was deeply moved by the second duel and enacts a new peace treaty in which the spoils promised to the winner were evenly distributed between both clans. He also recoves the battle scroll from Ieyasu and secures it in a hidden alcove of his Japanese-style Big Fancy House, so that the memory of the 20 chosen ninja would not be completely forgotten.
Nankoubou Tenkai: A Tendai Buddhist monk and political adviser for the Shogunate, he suggested to Ieyasu that since the Tokugawas are a military family, the succession dispute should be settled though some sort of organized duel between ninja instead of valued samurai. As the duel between the Koga and Iga rages on, Ieyasu sends him into the inner castle to keep the peace between Ofuku and Oeyu. He later returns in Basilisk's sequel series, The Yagyu Ninja Scrolls, where he takes on a more saintly role. He is the twin brother of Ashina Dohaku, who serves as the main villain in the second half of The Yagyu Ninja Scrolls.
Yagyuu Munenori: A Kenjutsu instructor of the Yagyū Shinkage-ryū school, of whom the Tokugawa Shogunate was a loyal patron. He was among the audience that witnessed Yashamaru and Kazamachi's duel at Sunpu and follows the war alongside Ieyasu. Because of their barely reined hostility to each other and the awesome power of their techniques, he views the ninjas of Kouga and Iga as being more akin to demons than humans.
Ofuku aka Lady Kasuga: The godmother of Takechiyo and leader of the faction supporting his claim to the Shogunate. A cold and heartless woman who murdered her husband's mistress and illegitimate child when they're brought into the household, Ofuku's only redeeming grace is her devotion to her protege Takechiyo whom she considers a surrogate son, at one point even risking her life to save his when the Kunichiyo faction poisoned him., Ofuku attempts to personally intervene despite orders from Ieyasu to the contrary, taking the side of the Iga and forcing Oboro into many problems. After witnessing Oboro's suicide, Ofuku rashly orders her samurai to asassinate Gennosuke, only to witness them die at the hands of his dojutsu. Although Gennosuke decided to spare her life, Ofuku is mentally crushed after the Iga's apparent loss; as punishment for her scheming, Hattori Hanzo decides to keep her in the dark regarding how Gennosuke abdicated victory.
Kunichiyo: Ieyasu's second grandson, represented by the Kouga. Although the younger of the two brothers, Kunichiyo's intelligence and cleverness has caused many within the government to view him as more deserving of the Shogunate over his elder sibling. He will grow into Tokugawa Tadanaga.