Jay: Ninja of Lightning was a Ninjago book released in 2012.
The Dragon's Roar
While at the entrance to the Fire Temple, Kai, Jay, Zane, and Cole discuss a method of getting to the Underworld. After pointing out that the legends implicate that someone can only a ride on one of the dragons if they share the same element, he proceeds to have Flame summon Wisp, Shard, and Rocky. Even as the Ninja attempt to negotiate with the remaining dragons, with Zane making an argument with Shard that it would be logical to defeat Garmadon, Jay attempts to talk with Wisp, only for the latter to lash out with a lightning bolt. Jay then proceeds to attempt to soften Wisp up with jokes and a salad, only for that to fail similarly. Finally, while brainstorming possible options, Jay ultimately gets the idea to build a roar amplifier for Wisp, satisfying the Lightning Dragon as it is now the loudest of the four, cementing its alliance with the Ninja.
While traveling on mules and looking for supplies, Kai and Jay drop by a general store named Lee's Supplies, only for the titular owner to suspiciously close early, forcing the both of them to take momentary residence in the nearby village's inn. There, they meet other villagers such Mrs. Park, the innkeeper; Din, a trader who works with Lee; and Lu, a fellow villager. From the three of them, Kai and Jay hear tales of Lee swindling all of them with faulty goods, and afterwards go to bed.
However, awoken by a crash outside, the two, alongside several villagers, discover that Lee's shop has collapsed on him, placing him in a coma, to his wife's grief. The next morning, Kai, Jay, Din, and Lu proceed to investigate the wreckage of the shop and discover that the support beams had been smashed through by someone, and upon discovering torn pieces of red and blue fabric, the two Ninja are suspected of the crime.
Luckily, due to their status as Master Wu's apprentices, the two of them are trusted with a single day to prove their innocence. Later on, the two of them visit Mrs. Lee's residence, and after noting the strange marks carved into several of the nearby trees, learn that Lee would often head back to his shop at midnight, usually with a random alibi to do so. Suspecting him of having been meeting someone those nights, Kai and Jay go to the shed where Lee keeps his shop records, and discover that he had been buying more goods than he had sold, enough to supply a small army.
Before they can investigate further, though, an unknown perpetrator throws a torch inside the shed, forcing the two of them to escape using Spinjitzu as the resulting fire destroys the records. Even as they recuperate, they're approached by the village elder Soon and are told that several Skulkin had been spotted in the nearby woods. In order to defend them, Jay creates special devices that magnify the yells of the villagers, fooling the Skulkin scouts into believing an army awaits them and scaring them off.
In return for their service, Kai and Jay are told by Soon that they had spotted the Skulkin in the woods a few times before as well, only to be interrupted by Mrs. Park, who reveals that in their absence the Skulkin had managed to kidnap Din, leaving behind his dagger, which Kai inspects.
As they prepare to rescue Din, Kai and Jay are informed by Lu of rumors about Lee making deals with bandits by selling them his unused goods. After Kai identifies that the marks on Lee's trees were made by Din's dagger, indicating he had been contacting him through the marks, Jay proceeds to spy on the Skulkin in their camp at night.
Spotting Nuckal and Wyplash conversing, he discovers that they had been expecting crates of supplies for them in the woods. After nearly having his hiding place exposed by a bird, which he silences with a piece of bread, Jay returns to the village to begin his plan.
In the morning, Jay finishes a device he had built and orders the villagers to stand by as the Skulkin return, and as he expects, they take their supply crates from Lee's broken shop and leave without bothering the villagers, at the same time dropping Din off. Even as Kai reveals that he rigged the crates with explosive powder, the supplies detonate off in the distance, incapacitating the Skulkin while he and Jay begin their plan to reveal the criminal.
Later on, the two of them gather Lu, Din, Mrs. Park, and Soon and explain why the four of them are suspects. After Jay reveals that the device he made is a Truth-Seeker meant to reveal the culprit, Din suddenly runs away, exposing himself for his crime. Even as Kai chases after him, he manages to learn the truth of what happened; Lee had indeed been making deals with criminals, including the Skulkin. Likewise, he had also made several deals with Din, only for the latter to be swindled multiple times. To gain revenge, the latter had caused Lee's shop to collapse on him, but at the same time this kept Lee's Skulkin customers from getting their supplies, and as a result they kidnapped him.
In the end, Jay subdues Din with Spinjitzu, allowing the other three former suspects to arrest Din. Jay proceeds to reveal that he had merely bluffed about the Truth-Seeker, and after getting their supplies, he and Kai leave to rejoin the rest of their team.
Book's official description
Masters of Spinjitzu: a new force to save the world!
Jay is much like the element he represents: fast and full of energy. Always good in a fight, always up for a laugh, and always, always inventing. Even if those inventions don't always turn out the way he wants!
Sensei Wu has gathered a powerful team of Ninja warriors. Now he must train them in the ancient art of Spinjitzu. If he fails, Lord Garmadon and his evil skeleton warriors will destroy the land of Ninjago and all of its inhabitants.
Faced with such a serious task, the Ninja have little time for laughter—that is unless Jay, Ninja of Lightning, is nearby. An inventor at heart, Jay never loses his sense of humor, even in the middle of battle. But when Jay laughs in the face of danger, will the joke be on him?
Way of the Ninja · Masters of Spinjitzu · The Golden Weapons · Rise of the Snakes · A Ninja's Path · Pirates Vs. Ninja (Book) · The Green Ninja (Book) · Attack of the Nindroids · Techno Strike! · The Titanium Ninja (Book) · The Rescue Mission · Ninja vs. Ninja · Spy vs. Spy · The Quest for the Crystal · Return of the Djinn
The Challenge of Samukai · Mask of the Sensei · Rise of the Serpentine · Tomb of the Fangpyre · Kingdom of the Snakes · Warriors of Stone · Stone Cold · Destiny of Doom · Night of the Nindroids · Who is The Phantom Ninja? · Comet Crisis