Our story unfolds during the twentieth century first decades. Lili is the beloved daughter of a young army officer who had been sent to the eastern front of battle in Asia. Before leaving to war, his father left her in the hands of his best friend, Master Yuki. Yuki is an ancient professor in the martial arts and he owns a preparation school for ninjas. While living with Yuki, Lili has been taught how to behave and fight as an experienced ninja and she is engaged in the practice with other students in a regular basis, despite her young age (she is eight years old). She is practically a senior herself. To complete her proficiency Lili has to pass a final test and the so expected day arrives at last. She'll be defied by a dozen skilled ninjas and she must fight them all at the same time in Yuki's training Japanese garden.

She knocks them down one after one, but when facing the last ninja she looses focus by dropping her father's picture, carefully placed in her outfit earlier that day, on the ground. She is defeated. At this very same moment, Yuki gets a letter from a messenger. It says Lili's father is missing after a bloody battle. He had been orientated by Lilis father to send Lili back to her native country to be raised by her only relative alive, the wealthy aunt Morgana, if anything bad happened to him. Master Yuki follows his friend's orders, but he worries Lili might be unhappy now that she is a total orphan. More than that, her preparation as a ninja is not complete, lacking what is most important of all: maturity to use it with wisdom. He decides then to send a guardian not only to protect but also to end her ninja preparation. For that task he already counts with a volunteer: The Warrior Didi. However, Didi is an untraditional ninja by being often clumsy when performing his duties, and Master Yuki becomes uncertain if hell be able to fulfill his expectations. Didi tries to convince him by the fact that hes got Caucasian facial features and that Lili doesnt know his face (all the students use masks). Yuki agrees but first Didi must show him he has gotten ninjas skills to do so. The master orders his students a sudden attack against Didi.

Didi defeats his opponents using a hilarious martial arts choreography, where his creativity using the garden elements like bushes, bowls and bamboo sticks are more valuable than his fight craft itself. Didi ends up as the winner, but Yukis training center is destroyed. The old master sees no other choice than sending Didi overseas to protect the little girl. However, he emphasizes Didi should only interfere when by no other means necessary, just to keep her safe. Lili must learn how to make right choices. Didi agrees and prepares to leave to the same address Lili was given without knowing shell count on extra help. Didi tries a triumphant exit by throwing one of that typical smoke effects on the floor, but spite of disappearing Didi shows up dressed as a geisha when the smoke fades away. He tries again and now he appears dressed like a samurai. Yuki shakes his head sideways (Didi is really a lost case...).

A couple days latter Morgana is taking care of her valuable Chinese art craft collection when she receives a letter from master Yuki about Lilis arrival to live with her. She gets mad with such unpleasant news and throws the letter as a ball paper of the window, hitting the new gardener, recently hired... Didi.

He falls down the ladder he was up, starting a chain reaction of funny events (he steps on a rake that hits him on the face, rolls himself with a garden hose spreading water over the people standing on the sidewalk, and so on...).

The gorgeous housekeeper helps him. Didi, totally dizzy, asks her the plate number from the vehicle that has hit him. She smiles and tells him their boss is upset because a not welcome niece is on her way to live with them. Lili arrives and is welcome by Yolanda and Didi. Very shortly after her arrival she gets to know that her aunt doesnt like children by the fact Morgana was humiliated in her wedding day when her fiancée Dr Marcos left her alone in front of the priest. There was a woman in delivery labor needing him. Dr Marcos didnt take in account she was poor and didnt have money to pay him. He followed his medical oath and saved the childs live, but not the mothers. Morgana never forgave him mainly by the fact she was dumped because some poor newborn child needed her fiancée. What about her needs? Morgana decides to get even with destiny by mistreating her niece, transforming Lilis life into hell. The little girl is accommodated into the smaller and hottest room in the house, the attic, and many domestic chores are immediately assigned to her, but she faces her new situation in a good mood, softening Didi and Yolanda's hearts. One of Lilis tasks is cleaning Morgana's expansive and rare Chinese art craft collection exposed in the living room.

As the time goes by, Didi falls in love with Yolanda who gently refuses Didi's affection because she is engaged to a soldier who is fighting in the same war Lilis father is missing. They dont know but, even before Lilis arrival, the house has been watched by one of Jacks gang boys. Jack is a heartless thief who uses young orphans to con people on streets. Among the boys is Daniel, a good heart kid that continuously confronts Jack, refusing to commit those crimes. Jack is always harassing and even beating him in order to follow Jacks will. Jack decides to show to his followers how to make a real theft and lead the kids one night to watch him breaking in Morganas house. He succeeds and forces all adults in the house to stay in the kitchen. A hilarious scene unfolds when Jack tries to tie Didi up to a chair but Didi keeps getting easily loose from it using his ninja skills. Jack doesnt understand and tries again and... again. Didi appears by his side asking about something totally irrelevant. Eventually, Jack uses a chain to maintain Didi glued to the chair. Suddenly the lights go of and a mysterious little black figure (Lili in her ninja outfit) attacks jack in many ways, making him defenseless. He finally hits the little ninja, but Didi helps the girl without her knowing that. Jack flees of the house in a humiliating situation in under the gangs eyes. Jack promises revenge.Certain day, Lili goes shopping for her aunt and gets to know Daniel. Hed been forced to con the little lady by his fellow gang members, but in the last minute he regrets it raising the fury of the boys. They invest against Daniel and he throws Lili into a small alley to defend her. At the moment Daniel is being beat the little ninja shows up again and defeat the gang. They run away. Lili quickly change her clothes and knees by Daniel side to make sure he is alright. Affection sparks between them (he does not recognize her as the savior ninja). She takes him to medical care in a small office close by and no one else but... Dr. Marcos is the physician. He eventually finds out Lili is Morganas niece and gets melancholic by the sadness of his own story. Lili knows she cant leave Daniel to join the gang again and decides to hide the boy in her aunts house, counting of course with Didi's help.

Another very funny situation is presented as follows: Morgana is the Ladies Society President and she is receiving several of those ladies for a tea in her house. Didi, Lili and Daniel try to mix and mingle using some of the clothes left in the entrance of the house by the guests.

Lili climbs on Daniels shoulder and they use a kind of robe that makes her look like one of the ladies. Didi wears a few of the items himself and, while crossing down the hall to get to the stairs and to the upper floors, he is constantly stopped by one of the ladies who ask him questions about their philanthropic ideals getting from him the most funny answers.

However Didi accidentally steps on the kids' robe and they get caught by Morgana, who demands an immediate explanation. Lili clarify the recent events and begs to Morgana to offer a shelter to Daniel just for a little while. Feeling the pressure of the ladies present in her house at that moment Morgana sees no other solution but accept the boy. They all celebrate and Daniel says he will stay only if he could pay by working in the house. Morgana says to herself: You bet.... Things seem to be running smooth in Morganas house when Jack finds out that Daniel now lives with the very same people who humiliated him. He prepares an evil plan to incriminate Daniel for robbing one of Morganas necklaces. Didi, Yolanda and specially Lili get very disappointed with the possible betrayal, although Daniel swears his innocence. Daniel is arrested, but Jack cleverly rescues him with the gang help.

Jacks evil plan goes deeper: he convinces Daniel that not even his best friends believed him and says to the boy only he, Jack himself, is his true friend, always there to protect and watch over, not only him, but everyone from the gang kids. Jack then inflames Daniel for revenge and counts on the boy for a new strike against Morganas place. Jack did not know but Didi and Lili are hidden behind a few boxes and carefully listen to the whole conversation. The night falls and Jack, now in the company of two thugs (Jack boroughed cash from a speculator), quietly approaches Morganas house.

From the attics window Lili observes the movement down there, while dresses up her second identity: The Little Ninja. Jack sends Daniel first. He is smaller and already knows how to break in and easily open the door for the other three thieves. It wont be hard to get to the valuable jewelry, Jack thinks. Once in the living room, Daniel is surprised by a grown up ninja (Didi). Daniel rushes to explain that his intention is to get Jack and the others arrested and that the ninja, whoever is him, must call the police. In a very fast move, the ninja gets Daniel and locks him into the closet under the stairs. Daniel does not understand what is happening and who is that strange figure. He shouts out for help, but no one hears him.

The bad guys enter the house and they also are surprised by the adult ninja. Jack orders the attack and an incredible fight choreography takes place. At the same time Didi hits the opponents he has to preserve intact Morganas art collection. Everytime we think something is gonna break Didi grabs it and still hits one of the bandits.

Lili, dressed as the little ninja, reaches the top of the stairway eventually and gets confused. Who the heck is that mysterious ninja down there? Didi is distracted by Lilis arrival and is punched down by Jack. As he faints to the ground Didi pushes a column and the vase on the top starts a domino effect, destroying one by one all the other artifacts. Lili shifts Jacks attention to her and the three men climb the stairs up in her direction. In their way up they meet Morgana that has been awaken by noise and faints to when sees the thieves and, mainly, her collection completed destroyed. Lili runs to the roof, followed by Jack and the thugs. When the men get to the roof Lili applies a strait kick that throws them over the edge and right on the rose bush in the garden. The police arrives to arrest the three thieves, but Jack still have time to throw his tool (the one he uses to force passage trough doors) in Lilis direction. She looses balance and falls down on the garden ground.

She is surrounded by Morgana, Yolanda, Daniel (he escaped from the closet), the gang kids and finally Didi, still trying to recover his senses (without his ninja outfit). Daniel takes her mask of and all of them are astonished. They panic when find out that Lili is the heroic little ninja. They try to wake her up, but she does not. Morgana asks for forgiveness, after all she was really mean to her niece. Lili stays unconscious. Didi realizes he failed in his mission to protect Lili. She opens slowly her eyes and there is a general relieve she is not dead.

Some time has passed. Lili is lying on the best bed in the best bedroom of Morganas house. Their relationship has improved a lot. Dr Marcos is now paying medical visits to his newer patient and that brings up old feelings about Morgana.

He says to Morgana that Lilis clinical status is stable, but he is afraid shell never walk again. Morgana is emotionally destroyed and she decides to ask for Marcos' forgiveness as well. Shes been unfair and bitter with him during all this years. Now she understands his valuable mission as a doctor. Marcos declares his love to her and propose marriage once again. She accepts.

The boys (no more as a street gang) pay a visit to Lili and one of them asks her to be their martial arts teacher. She says yes but only if they use the knowledge for good. They enthusiastically accept. Didi decides to go back to Japan. He is devastated by Lilis situation. Before leaving, he goes to Yolanda and says he likes her a lot. She is flattered but again she talks about her fiancée, only this time she shows Didi a picture sent by him from the battlefield. Didi looks closely to the picture and notices that Lilis father is also in the picture, standing by Yolandas boyfriend. She says the picture was sent a few days before. When Didi gets back to Japan he is afraid Master Yuki will send him away because he failed in his mission. After all, Didi has no other place to go. However, our hero is surprised by the warm reception he gets from Yuki. He says he doesnt understand because Lili will not walk anymore.

Yuki explains Didis mission was to make Lili happy and so he successfully did. Didi feels better, but says his mission will be complete only when he put Lili and her father together again.

Morganas wedding day arrives. She and Marcos decided to adopt all the ex-gang boys and they are all dressed up for the ceremony. Lili is sat on a chair on the front row. She can not walk yet, in spite of the revolutionary treatment she went through, paid by her aunt. Suddenly Didi (dressed in a kimono) burst into the room followed by two men in armys uniform. Yolanda recognizes her fiancée and runs in his direction. They kiss. Lili looks to the other man, who looks her in the eyes. He is shaked by Lilis faith, but the little girl slowly starts to get up the chair. Everyone in the room is breathless. Lili walks to her fathers arms and she hugs him tightly.

Everybody has tears in their eyes.

Didi now feels hes completed his mission and quietly leaves the room. He is already outside when Lili reaches him. She hugs and kisses Didi and thanks him for having made her the happiest girl in the whole world. Didi is flattered. He decides to make one of his triumphant exits by throwing a smoke effect on the ground. When the smoke fades away the audience sees Didi dressed only with a sumo like underwear. He waves to the camera and walks away by foot.