Sensei Wu is the younger son of the First Spinjitzu Master. In Wu's childhood, he and Garmadon were the best of friends. One day in his youth, Wu lost his father's katana during a spar, and Garmadon climbed over the wall to retrieve it. While outside, the Great Devourer bit Garmadon's hand, corrupting him with its venom. As a result of the growing evil within him, Garmadon became increasingly distant from his family, but he and Wu would remain civil with each other for some time. When Garmadon married Misako and fathered Lloyd, Wu was happy for his brother, but also somewhat melancholy, as he personally harbored some affection for Misako.
After their father died, Garmadon and Wu vowed to protect the Golden Weapons. Garmadon, however, planned to steal the Weapons, but when he tried, Wu confronted him and they fought. Wu won the battle, but at a cost. The kimono he was wearing had a protection spell to keep him safe from evil. This in turn worked on Garmadon, and cast Garmadon into the Underworld, banishing him for what could have been eternity. Knowing his brother's ambition to get all Four Weapons, he sealed each one away and placed a guardian to protect each individual one.
As a Hero
He heads to Ignacia. There, he walks into Four Weapons. He encounters Kai, and he gives him an attitude. Sensei Wu feels potential in Kai. The Skulkin Army, led by Samukai arrive. Sensei Wu and Samukai fight, and Nya is taken. He takes Kai to the Monastery of Spinjitzu. Kai passes the training, and Sensei Wu goes to rest.
Kai is confronted by Jay, Cole and Zane in a fight. The fight ends abruptly when Sensei Wu appears, soon declaring the elements each ninja possesses and giving them their colored robes. The next day, Wu makes the ninja pull a horse carriage (with him inside) to the Caves of Despair. He warns the ninja not to use the weapon, only to be cut off by Jay. Later, after the ninja have recovered the Scythe of Quakes, he chastises Kai for using the weapon to fend off the Earth Dragon, before setting off for the Frozen Wasteland in search of the Shurikens of Ice
As the ninja sail through the wastelands, "drifting aimlessly for miles" Wu has taken a perch on the dragon sculpture at the front of the ship they are using, Wu unexpectedly turns around and teaches the ninja about the Tornado of Creation, before the ship crashes into the Ice Fortress Later, he sends the ninja alone to retrieve the Nunchucks of Lightning from the Floating Ruins while he prepares a camp in the Forest of Tranquility. When the ninja glide from the Ruins to the camp, Kai tries to get Sensei to dance with them, only to have Wu comment that they needed to get their sleep. Wu gave in, and started dancing until Zane made a joke about it, and then continued to the laughter of the other ninja. After Kai left for the Fire Temple, Wu followed him in secret and fended off a small army of shadows, until sacrificing himself to prevent Samukai from getting the Dragon Sword of Fire
Upon arrival in the Underworld, Sensei Wu headed straight for Lord Garmadon's Dark Fortress, where he confronted his brother in the throne room. He easily defeated the Skulkin soldiers sent after him, but soon faced a far greater challenge: Samukai, wielding the other three Golden Weapons. Sensei Wu fought hard, using the Sword of Fire to great effect, but Samukai's use of the other Golden Weapons overwhelmed him, leading to his defeat moments after the Ninja broke into the fortress themselves.
As Sensei Wu recovered his wits, Samukai took the Sword of Fire and challenged Lord Garmadon for the throne of the Underworld. However, Garmadon simply laughed, revealing that the power of all four Golden Weapons was too much for anyone - even himself - to control, and Samukai was disintegrated as the weapons formed a portal. As Garmadon prepared to enter the portal, Sensei Wu tried to reach out to his brother, claiming that their father would not have wanted any of this to happen. His pleas were rebuffed by Garmadon, who revealed that his real plan was to trick Samukai into using all four Golden Weapons at once, thereby creating a portal to a realm where he could find the power to safely wield the powerful weapons himself. With that, Garmadon fled through the portal, leaving Sensei Wu and his pupils to gather the Golden Weapons and return to the mortal realm.
Sensei Wu finds the Ninja playing a video game, upset at the fact they're neglecting their training, he unplugs the video game and scolds them. He begins to speak about the power of the Golden Weapons, when Nya interrupts, stating that Lord Garmadon is in Jamanakai Village. The Ninja rush to their Dragons, displaying the fact they're not in peak shape, and set off to face Lord Garmadon. After the Ninja find that it was just Lloyd Garmadon they discover the legend of the Green Ninja through one of Sensei Wu's scrolls. To determine the identity of the Green Ninja they set up a tournament. In the second round of the Green Ninja tournament, Kai's sword bursts into flames, and Sensei Wu quickly rushes outside. He uses Zane's Shuriken to put out the fire, and once again scolds the Ninja. Sensei Wu then returns to his Spirit Smoke to see that the Serpentine have invaded Jamanakai Village. He tells the Ninja of what he saw and sends them to save the village. After the battle between the Hypnobrai and the Ninja, Sensei Wu arrives to talk to the Ninja. Before the episode ends, he returns to the Monastery.
Once again, Sensei Wu's meditation was interrupted by his pupils' noise-making, but he was pleasantly surprised to find them in the training course rather than the game room. He dissuaded the Ninja from questioning Zane's odd behavior and tried to comfort Zane when he became melancholy over not knowing his origins. Later, Sensei Wu ate dinner with his pupils and was dragged into a friendly food fight.
The next day, the Ninja set out to Wildwood Forest on a tip from Zane, who had stumbled upon Lloyd's Treehouse Fortress after following a mysterious Falcon. Sensei Wu initially remained at the Monastery of Spinjitzu with Nya, but only so he could prepare himself for the battle against the Serpentine. He and Nya flew to the forest astride Flame's back, only to find the fortress crumbling and Cole attacking his allies (due to Skales' hypnotism). Recognizing the signs of Hypnobrai Hypnotism, Sensei Wu played the Sacred Flute, breaking the spell and allowing the Ninja to escape the fortress moments before it collapsed completely.
On their way back to the monastery, Sensei Wu explained the flute's significance to the Ninja, claiming that it would play a large part in the defeat of the Hypnobrai. When Flame returned to the monastery, the group was horrified to see it completely destroyed - the Hypnobrai had burned it to the ground after retrieving their staff. As the Ninja rushed to free the other dragons from their burning stable, they blamed Zane for their loss, prompting Sensei Wu to rebuke them for their rash anger. Before the Ninja could apologize, Zane had already flown into the night on the back of his dragon.
Despite the loss of their home, Sensei Wu remained optimistic as he and his pupils erected a meager shelter from what they could salvage from the monastery. The next day, Zane returned and explained that the Falcon had led him to a new home: the Destiny's Bounty. As the Ninja rushed to explore the ship, Sensei Wu promised that they would help Zane find his family, only for Zane to reply that they were his family.
As the Ninja worked on restoring the Destiny's Bounty, Jay's parents, Ed and Edna, came by to visit their son. Sensei Wu watched in amusement as Jay struggled to remain calm despite his parents' embarrassing antics; commenting afterwards that the Blue Ninja could teach them all "the art of kissing pillows". The next day, he noticed that the Ninja's dragons were molting, and told his pupils that the beasts would have to go to the Spirit Coves to complete their metamorphosis.
After seeing the dragons off, Sensei Wu joined the others in walking to Ed & Edna's Scrap N Junk so Jay could visit his parents. Upon arrival, they found the owners stuffed in a fridge, slowly transforming into snakes. Sensei Wu immediately realized that Ed and Edna had been bitten by the Fangpyre tribe, a suspicion confirmed when the Fangpyre revealed themselves, along with Lloyd (who had released them in hopes of getting revenge on the Hypnobrai who betrayed him).
The Ninja immediately jumped into battle, fending off the snakes and their new vehicles while Sensei Wu began playing the Sacred Flute to weaken the Serpentine. Unfortunately for him, Lloyd drowned out the music with a Fangpyre-infected boombox; when Sensei Wu demanded that Lloyd stop that, his evil nephew simply turned up the volume and claimed not to hear his words. In the confusion, Sensei Wu was almost bitten by a Fangpyre Scout, but Edna knocked it out with a frying pan.
The Fangpyre were eventually forced to retreat, but their staff was still in the hands of General Fangtom. To save Ed and Edna, Sensei Wu told the Ninja about the Golden Weapons' ability to transform, and the Ninja soon manifested vehicles of their own with which to pursue the fleeing Serpentine. Jay managed to retrieve the staff, but his inexperience with his new vehicle caused him to lose focus, reverting the jet to its original form. The other ninja soon followed, and the group barely escaped back to the Destiny's Bounty with the anti-venom.
The ninja realize they may have reached their full potential, and accidentally disturb Wu while he is packing. He tells them the story of how and why Garmadon was bitten by the Great Devourer and turned evil, before telling them they have completed their training. He then leaves for Mystake's tea shop for Traveller's Tea, and uses it to travel into the alternate dimension Lord Garmadon had escaped into in search of his help in getting Lloyd back and defeating the Serpentine.
Garmadon confronts Wu and a battle ensues, with Garmadon summoning the Mud Monsters to consume Wu. Wu tells Garmadon that Lloyd is in danger, and Garmadon rescues Sensei just in time to prevent him from dying. They then journey to the Mountain of Madness.
Upon reaching the Mountain, Wu and Garmadon climb up, encountering the Craglings. They defeat the Cragglings, and climb up to the top and escape through a vortex back to Ninjago.
After returning to Ninjago Wu brought Garmadon to the Bounty, much to the dismay of Kai.
Sensei Wu is consumed by the Devourer, and is only seen at the end of the episode after Garmadon destroys the Great Devourer. He finds his tea kettle among what is left of the Devourer, commenting that it is still hot.
Sensei Wu and Nya leave on a one day road trip to get medicine for the Ultra Dragon and some other things, and returns just in time to save Lloyd from Skales who was plotting to kidnap him and convince Garmadon that he (Skales) should be in charge.
Sensei Wu saw the Ninja off on their mission to the Ninjago Museum of History, where Lord Garmadon was attempting to revive a Grundle. When the Ninja did not return from their mission (due to being de-aged into children as a side-effect of Garmadon's spell), Sensei Wu joined Nya in searching for them. Their efforts proving fruitless, the duo returned to the Bounty, only to find a message from Lloyd, asking them to meet him and the Ninja at the Doomsday Comic Book store.
Putting some of the pieces together, Sensei Wu has Nya accompany him to Mystake's tea shop, where they request some Tomorrow's Tea. Due to Mystake having trouble finding the tea, Sensei Wu and Nya did not reach the comic book store until nightfall, finding the Ninja at the mercy of the revived Grundle. After Lloyd uses the Tomorrow's Tea to restore the Ninja and defeat the Grundle, Sensei Wu witnessed the Green Ninja aging into a young man along with his friends.
Wu and the ninja travel to the Museum after the Devourer's venom has made the Museum's gift shop bobbleheads come to life. One escapes, and Wu races after it, crushing it with his foot, only to turn around to find Misako, who is Lloyd's mother, greet him. When the giant Stone Warrior is unveiled, the Devourer's venom drips on it, bringing it to life. Wu and the other escape it for a short period while Lloyd works on a trap. Misako finds Lloyd, and Lloyd tricks the warrior into standing on top of a piece of paper covering up the bottomless pit it was found in. Wu invites Misako to join the ninja, and she says only if her son allows it. Lloyd allows her to, and she lives with the ninja from that point forward.
While the ninja train Lloyd, Sensei Wu takes his hat off to look at a photograph of he, Garmadon and Misako. Misako unexpectedly appears behind him and startles Wu. Misako shows him her research and the scrolls containing the prophecy of the Green Ninja. Moments later, an earthquake shakes the Bounty (the Bounty was parked on top of Dareth's Dojo) due to the Serpentine literally undermining Ninjago city. The Serpentine unlock an ancient tomb containing the Stone Army and the Devourer's venom awakens them. The serpentine are then trapped underground again, seemingly forever this time. After the Stone Army reveals themselves, Misako suggests making the NGTV tower an evac station for the Bounty to land on. Wu and majority, if not all, civilians left in the city and the ninja climb up the stairwell. Misako loses the container her research was in, and goes back to get it. Once everyone (excluding Misako) is on board, the Stone Warriors start destroying the Bounty's engines, and Wu leaves at the last moment to save Misako as the Bounty flies off. Misako gets to her research, but at a cost; she is now dangling off the side of a 20-story high stair well. Wu fights his way through the Stone Army and gets to Misako at the last moment and saves her. They are only left with one choice after the Army backs them into a corner. Zane senses that Nya should fly the Bounty downwards, and orders her to do it. Wu and Misako jump off of the building, and land on, to their surprise, the Destiny's Bounty.
Sensei Wu sends the ninja out to find the Temple of Light while he, Dr Julien, Misako and Lloyd stay back to work on vehicles for the ninja. They complete the vehicles, (the Earth Driller and the Fire Mech) before sending out the ninja to the Temple. When Lloyd uses the "Golden Dragon," Wu, Misako, Nya and Julien are watching inside the Bounty and Wu is embraced by Misako.
After the Overlord was defeated, Sensei Wu acquired Darkley's Boarding School and turned it into "Sensei Wu's Academy," of which he became headmaster and the ninja, (along with Nya and Dareth) become teaches.
Becoming Techno Wu
Wu is taken back to Borg Tower where the Overlord probes his memory to find where the ninja are hiding. eventually the he gets turned into Techno Wu one of the Overlord's Newest Minion
- At first Wu is one of the protagonist with his brother Lord Garmadon as one of the antagonist until Garmadon is freed of the corruption and became one of the protagonist and Wu becoming one of the antagonist after being transformed into Techno Wu.