300 years ago, Yagyu Jubei was the greatest swordsman Japan had ever seen. His feats were legendary. But eventually he started getting old, and he didn't have an heir. Despite his style of swordsmanship being the standard, nobody quite did it correctly. He didn't want his technique to be lost, so he somehow bound it up into an eyepatch shaped like a heart. He sent his most trusted servant to find the one who would be able to access the eyepatch — he would know them by their "plump bouncy bon bons." The servant, Odago Koinosuke, left on the geas that he would find the next Jubei if it took the rest of his life, and beyond.
Unfortunately, the original Jubei's fame did not come without a price. The Yagyu family crushed all other schools of swordsmanship and slaughtered any who continued to resist. Jubei himself died in a battle with the teacher of the last school to fall, Ryujouji Daigo.
The Ryujouji clan and school swore an oath, that they would never forget what was done to them, and they and their descendants would wipe out anyone who would take up the name of Jubei. Not even death would stop this pledge.
300 years later.....
Enter Jiyu Nanohana, an Ordinary High-School Student...yeah. She's rather happy with her widower father, Sai, and her friends at school. She even has a cute nickname, Jiyu-bei. ...say it fast and it sounds like "Jubei." Isn't that funny?
This changes when she's approached by a rather strange looking guy in antique clothing, who says that she is the Chosen One, and if she would please accept this Lovely Eyepatch?
And thus, she becomes Jubei-chan, the second incarnation of Yagyu Jubei! Pity there isn't any evil around. Oh, wait. The Ryujouji School has been waiting for 300 years for this little bit of payback.
Obviously, Jiyu wants nothing to do with it. It's a circular problem. But the Ryujoujis won't listen. Also, their grudge is so powerful that it infects their souls. In order to save them, Jiyu finds a way to modify the Jubei technique, and make a sword technique that cuts the hate and undeath out of their very spirits. Those cut are freed to assimilate into the modern day and forget the past.
Nevertheless, can she take on the entire Ryujouji Clan and still be Jiyu, or will she get caught up in the bloodshed that occured 300 years ago?
There is a second season, Jubei-chan: Revenge of the Siberian Yagyu. In it, another dead clan, this time a splinter group of the Yagyuus, want revenge on Jubei. They are overshadowed, however, by another Jubei-chan! This one, Freesia Yagyu, is the biological daughter of Yagyuu Jubei, preserved for 300 years by being frozen in a glacier. She's very upset that her father's inheritance has gone to another girl — and she wants it back. She becomes simultaneously Jiyu's manipulative best friend and Jubei-chan's worst enemy; she knows who Jiyu is. Jiyu doesn't know who she is. The second season has, arguably, some of the greatest sword battles in all of anime.
- Anti-Climactic Unmasking: In the second season, Mikage pulls the face mask off of a mysterious antagonist, revealing nothing, since Freesia ages up when transformed.
- Arc Words: "Nisemono" from the second series, translated as either "imposter"note or "fake". The importance starts to appear in the episode "Peaceful in a Fake Family", where it becomes clear that Jiyu, Freesia, Mikage, and Sai are all hiding secrets from each other while trying to be a surrogate family. Later still, Freesia manages to provoke Sai into slapping Jiyu by claiming that she said her father's work was fake. When Jiyu eventually recovers from the Heroic BSoD provoked by this, she shows her character development by declaring that both she and Freesia are truly the successors of Yagyu Jubei — so neither of them is an imposter.
- Art Shift: Used continuously, and even for dramatic purposes — e.g. when the Plucky Comic Relief gets serious. In the second season each leading member of the Siberian Yagyu Clan is animated in a different style — one is in the show's normal style, one is in 3D CGI, one's drawn Super-Deformed using Thick-Line Animation, etc.
- This gets lampshaded by characters who the victims of an art shift to crude line drawings during a single scene, by virtue of the plot moving away from them.
- Badass Normal: Shiro in the first series, Oozaru and Kozaru in the second series.
- Becoming the Mask: In the second season, Freesia's character development revolves around this, as she finds herself enjoying the role she adopts in the life of Jiyu and her friends.
- Bare-Handed Blade Block: The Mutodori; something the Yagyu family historically is credited to; is featured in the climax of the second season.
- Berserk Button: Freesia doesn't like it when Jiyu's called "Yagyu Jubei".
- Big Bad Friend: Freesia is very close to Jiyu as she plots to destroy her.
- Call to Adventure: Subverted. Jiyu hates having the eyepatch and tries to throw it away every chance she gets. Koinosuke often has to fish it out of the garbage. Somehow he always manages to find it.)
- Can't Catch Up: Lampshaded, in the second season, first season big bad Shiro confidently states that he who fought Yagyu Jubei as an equal in the first season will surely be able to at least be a challenge to this new enemy, only to be defeated instantly when he tries.
- Dark Magical Girl: Freesia
- Defeat Means Friendship: Justified; Jiyu is cutting apart the grudge against Yagyu Jubei, which is the only reason why they attack her in the first place. They are quite grateful for it.
- Deliberately Cute Child: Freesia
- Delinquents: Parodied— Bantarou and the Unrefined Trio.
- Demoted to Extra: Bantaro and Shiro in the second series; they're painfully aware of this.
- Disappears into Light: Any spirit that lets go of their obsession without being cut by Jiyu. Koinosuke in the first season, most of the Siberian Yagyu clan except for Nizaemon and Kita.
- Expressive Shirt: Bantaro's shirt, which displays kanji related to whatever his current mood or train of thought might be. Such as "idiot," "reckless" or "breasts."
- Extruded Book Product: Jiyu's father Sai makes a living ghost-writing Jidaigeki Samurai novels. In the second series, Jiyu asks him to stretch by writing a romance novel under his own name, which causes tension when he has to hide the fact he's doing another ghostwriting job on the side.
- Eyepatch of Power: The Lovely Eyepatches, of course.
- Freefall Fight: Happens in the second series between Freesia, Mikage, and Jiyu.
- Friend to All Living Things: Freesia
- Fusion Dance: Freesia and Jiyu fuse together in the last episode using The Power of Friendship, which somehow either turns them into or summons the Original 300-years-dead Yagyu Jubei. (The initial result was just a fused successor, given the boobs; Jiyu and Freesia are left on the ground, untransformed, once the original Jubei appears.)
- Gag Boobs: By Yagyu Jubei's own words, this is a defining trait to find his successor. Appearance-wise, Jiyu's fairly tame by modern standards.
- Healing Shiv: Jiyu's sword actually brings back the dead in addition to freeing their souls from their hatred. Most Magical Girl shows dealing with purifying Monsters of the Week give their heroine a magical wand that shoots sparkles and Stock Footage. Jubei just has a katana. Same results, hilarious visuals as the target very plainly gets cut down.
- The Heartless: The lost souls of the Ryujoji and Kita-Yagyu clans.
- Heroic BSoD: Freesia really does a number on Jiyu's sense of reality.
- Jiyu's subsequent rejection of Ayunosuke causes her to turn into a tree.
- Heroic RRoD: If Jiyu wears the eyepatch too long or fights too hard, she begins to fall into a magical fever that can't be cured normally.
- Human Popsicle
- I Owe You My Life: Mikage and her husband, towards Jiyu.
- Jidaigeki: Subverted.
- Kawaiiko: Subverted. Freesia acts this way to fit into society.
- Kid Samurai
- Magical Girl
- Meaningful Name:
- Not only does "Jiyu-bei" shorten to "Jubei", but Jiyu's name herself is a Japanese word meaning "Spiritual Freedom." IE, what she gives to the lost souls.
- It's also worth noting that Jiyu's mother was named "Makoto," which can be translated to "Truth," particularly since in Season Two, Freesia's mother is named "Trusia," furthering the parallel between both Yagyu descendants.
- Meta Guy: Bantarou, Shiro, Oozaru, and Kozaru in the second series.
- Mood Whiplash
- My Greatest Failure: Sai stayed at work — as his boss demanded — while Jiyu's mother was dying, and only made it back when it was too late.
- Ninja: Note, despite the English Market Based Subtitle of "Ninja Girl", Jubei isn't; she's a "Swordswoman". The only character who is referred to as a "Ninja" would be Mikagenote . Freesia wears a face mask so she may count as a ninja visually, though her fighting style (being a swordswoman like Jubei) obviously doesn't.
- Obfuscating Stupidity: Freesia Yagyuu only acts like a cheerful hick.
- The Ojou: Subverted. She and her Girl Posse are the Yuppie Couple of this series.
- Parental Abandonment: Subverted. Jiyu's father, Sai, goes Papa Wolf and insists on being involved once he finds out what's going on.
- Plucky Comic Relief: Oozaru and Kozaru, Bantarou's sidekicks.
- Refusal of the Call: Subverted. Not only is this one of Jiyu's defining traits, but this, along with being Messianic Archetype, turns out to be the key to her victory. Even so, she does have to accept the Call to escape it.
- Replacement Goldfish: Sai and Jiyu's relationships with Mikage, a Ninja who was the Evil Twin of Jiyu's dead mother.
- Rousseau Was Right
- Running Gag:
- Maro trying to take Jiyu and Sachi out to a dessert shop in town, only to be foiled by either Jiyu's other life interfering or by the store being closed for no apparent reason.
- Sai immediately shooting Bantarou or Shiro down if they try calling him "Papa", "Dad", "Otousan", or anything similar.
- Shout-Out: In season one, one of Jiyu's challengers is a crayon scribble named Tenchi Muyonosuke. Also a Take That!: Tenchi is short, ugly, with a nose that constantly drips snot and thick glasses, a voice like nails scraping across a blackboard, all the charming personality of a rabid wolverine, and is drawn in the style of a child's scrawl.
- Stepping Stones in the Sky: More like stepping logs, but who's counting.
- Stock Footage: The transformation sequences. Played straight in the first season, averted in the second.
- Talking Animal: A whole forest of them with who Freesia lives after thawing out and before leaving on her quest.
- Take That!: In addition to "Tenchi Muyonosuke" mentioned earlier, Sai briefly has an Imagine Spot of a gratuitous Love Hina knockoff Harem Comedy during a bout of writers' block in the second season. (He swiftly rejects the idea.)
- Training from Hell: Parodied in the first series. Koinosuke decides that Jiyu needs to learn how to function with one eye when she's in Jubei-chan mode, and so locks her in a one-eyed helmet that looks horrifyingly like a pink urinal. Hilarity Ensues.
- Traitor Shot: About a third of Freesia's scenes when she's near Jiyu or Sai.
- Transformation Sequence
- Twin Switch: In the first series, it's revealed that Shirou and his twin brother Hajime traded identities; the Shirou the audience knew Just Wanted To Be Normal, while Hajime thought being the heir to the Ryujouji clan would be fun. This fact gets used to set up a Your Princess Is in Another Castle! moment.
- Undying Loyalty: Koinosuke didn't let death stop his mission for the original Jubei, even for 300 years. His child Ayunosuke carries on the tradition in the second series.
- Verbal Tic: Parodied in the second series: Oozaru and Kozaru deliberately start using "-zaru" — "-Monkey" — at the end of their sentences, hoping it'll catch on.
- Gratuitous English: In one scene, they try to redo their tic in Gratuitous English to appeal to the foreign anime fanbase. "Monkey Morning!" "Little Monkey Morning!"
- You Can't Fight Fate: Subverted.