When Kukui was a young child, he was accompanied by his Litten. One day, they encountered Ash and Torracat, who came from the future. Kukui became excited to see Ash's Z-Ring, and he and Litten watched Torracat using the Fire-type Z-Move: Inferno Overdrive. Litten and Kukui became ecstatic and decided to challenge Ash and Torracat. Though the latter intended to have Torracat lower its attack power, Kukui wanted a real battle, as he didn't want to be treated like a kid. Litten attempted to use Ember and Bite but was defeated by Torracat's Flame Charge and Fire Burst. While Kukui was sad over his loss, Litten helped him regain his confidence, and was praised by Ash that it did its best in the battle. Suddenly, a giant Treverant appeared, which was a Totem Pokémon, who often sneezed. Litten helped the Totem Treverant, Ohji, feel better, and the group found out that a bunch of Cutiefly were atop of it. Just as Kukui and Litten descended down from Ohji to have a rematch with Ash and Torracat, the latter two disappeared. This made Kukui and Litten wonder where they went to.
Incineroar was Professor Kukui's main Pokémon under disguised as the Masked Royal. It was used to take down Machamp, Primarina, and Decidueye with a powerful Malicious Moonsault Z-Move. When Litten personally confronted it, Masked Royal let Ash, Sophocles and Kiawe face him in a Battle Royal. Charjabug used Discharge, while Marowak used Bonemerang, while Litten used Scratch on Incineroar. The latter resisted and blocked the attacks before bashing the Pokémon away on the ring. Marowak attempted to use Shadow Bone on Incineroar, who resisted the attack and hurled Marowak away. Incineroar easily took Litten, Marowak and Charjabug down with its Darkest Lariat. However, Litten survived and sensed that Incineroar was holding back its true power. Litten went to use Fire Fang, but Incineroar used Bulk Up and held Litten in its fist. Masked Royal saw that, and Incineroar's Throat Chop defeated it. After Ash had some training with his Pokémon, Masked Royal and Incineroar approached them. Incineroar challenged Litten to a battle. Litten attempted to attack with Fire Fang and Ember, which Incineroar blocked and retaliated with Throat Chop and Cross Chop. Litten's determination grew stronger, as it executed Flame Charge, only for Incineroar to grab him by his head. At that moment, Litten evolved into a Torracat and executed another Flame Charge, and Incineroar could not cope with its speed. Incineroar used Darkest Lariat to attack, but Torracat managed to inflict some damage to its right hand. To finish off, Incineroar used Bulk Up with Throat Chop, which defeated Torracat. Despite this, Torracat was even more determined to battle Incineroar someday, as it became his rival.
Incineroar battled against Mr Electric and his Electivire and used Throat Chop to attack it, only to be interrupted by an attack from Magmortar and then attacked by the Revengers' Pokémon. Due to interrupting the battle, Mr Electric was disqualified, though Masked Royal and Incineroar were not pleased to have won in this fashion. Incineroar participated in a tag team battle alongside Torracat against Electivire and Magmortar. Incineroar started off with Cross Chop, countering Magmortar's Flamethrower, followed with another Cross Chop against Karate Chop. Incineroar swapped sides with Torracat until Torracat got hit by Wild Charge. Incineroar used Bulk Up, followed with Darkest Lariat against Electvire, who retaliated with Thunder Punch. In the middle of the match, the Revengers' Muk and Poliwrath grabbed Incinroar's legs, but Lana and Kiawe fought them off. This inspired Masked Royal to win the fight fairly, as his Incineroar used another Darkest Lariat against Thunder Punch. After Torracat defeated Electivire with Revenge attack, Masked Royal had Incineroar use the Z-Move Malicious Moonsault to defeat the rest of his opponents. Viren interrupted the battle by sending a Pangoro, but they both were defeated from a combination attack of Torracat's Flame Charge and Incineroar's Darkest Lariat. Ash was pleased with the teamwork with Masked Royal, and wanted to have a match with him and Incineroar. The two agreed, but much to Ash's surprise, the two ran off in a hurry.
Kukui faced Gozu's Mega Aggron during his and Faba's critical situation on preventing Team Rocket's Matori Matrix Squadron from reaching the Ultra Wormhole. Kukui had no choice left, and asked Faba to keep the following secret from his class: he brought out Incineroar, who used Darkest Lariat to stop Aggron's Heavy Slam. Gozu had Aggron use Flash Cannon, but was defeated by Incineroar's Z-Move Malicious Moonsault. Faba realized Professor Kukui was the Masked Roya, and showed his shirt to show he was a big fan of that figure. Later, Kukui, Faba and Incineroar shared some of their Ultra Aura to Necrozma, to help it regain its light. In addition, the group awaited the Ultra Guardians' return, who succeeded in their mission to stop Necrozma.
One day,Masked Royal's Incineroar defeated Mad Magmar's Magmortar. After the battle, Masked Royal announced a tour across the town, starting from the mini Battle Dome on Melemele Island's mall. Since Professor Burnet wanted to visit the event with Ash and Professor Kukui, the latter visited Molayne, who devised a plan to be Masked Royal, so Kukui could be with his wife while they shake hands. On the day of the event, after Masked Royal had Incineroar demomstrate its Bulk Up and Darkest Lariat, he shook hands with the audience, until he saw Ash. Masked Royal announced a quick break, and passed his clothes and Incineroar to Molayne. In a strange turn of events, Faba and Team Rocket's James tied Molayne up, and due to Mad Magma's arrival for revenge on Masked Royal, Faba disguised himself Masked Royal. Though many didn't believe that was the actual Masked Royal, Faba had Incineroar use Darkest Lariat. Due to not being Incineroar's trainer, Faba was easily knocked down, after Magmortar used Fling on Incineroar. Thankfully, Molayne managed to get himself untied and had his Magneton disable to mall's electricity temporarily for Kukui to change to Masked quickly before they were spotted. Magmortar attempted to use Fire Punch, but was easily defeated by Incineroar's Malicious Moonsault Z-Move.
Burnet was cleaning up the closet when she found Kukui's photo of himself and his Litten (who eventually evolved into an Incineroar) when he was younger. Kukui became startled, but enjoyed looking at the photo, and told his Litten was actually being taken care of by his parents. As for Ash and Torracat, the two were sent into the past, where they met Kukui and Litten, to which Torracat recognized the latter to be Incineroar by its smell. Masked Royal and Incineroar appeared on screen, announcing the start of the Alola Pokémon League. The former also announced the winner of the tournament would have a special match with him and Incineroar. A poster featuring Masked Royal and Incineroar was posted on Manalo Stadium to promote the Pokémon League, which Team Skull grunts have defaced. The poster featuring the two was later cleaned up.
Before the battle against Ash began, Kukui spent some time with Incineroar by meditating. On the battlefield, Kukui sent Incineroar to battle Ash's Torracat. Torracat started the battle with Flame Charge, though Incineroar used Bulk Up to negate that attack. Torracat nevertheless continued using its move to boost its speed. Incineroar attempted to attack it with Darkest Lariat, but missed and got hit by Fire Fang. However, Incineroar knocked Torracat away, who continued circling around Incineroar with Flame Charge. Due to Incineroar's ability, it could sense where Torracat was, and dealt a Throat Chop to hit it away. Torracat retaliated with Fire Blast, which hit Incineroar, who used a Blast Burn. Much to Kukui and Incineroar's shock, Torracat absorbed the move, and the flames were stored into its bell. Just as Ash wanted Torracat to retaliate, Torracat could not hold such intense heat, and Ash called him into this Poké Ball. Ash sent Lycanroc out, who used Accelerock that hurt Incineroar. Next, he went to use Stone Edge against Incineroar, who was still recuperating from Blast Burn. In the last moment, however, Incineroar used Darkest Lariat to counter Stone Edge. Lycanroc grabbed a shard from the Stone Edge, and went to attack Incineroar with it, who used Throat Chop. However, Incineroar got hit from that attack, so Kukui called it into its Poké Ball.
Later, with his Empoleon defeated during the exhibiton match at the Pokémon League, Kukui sent Incineroar to battle Ash's Melmetal. Incineroar used Darkest Lariat, which countered Melmetal's Flash Cannon and hit Melmetal itself. Melmetal went to use Double Iron Bash, but Incineroar grabbed its hands and pulled it in, to quickly defeat it with Blast Burn. Kukui, however, called Incineroar in its Poké Ball to save it for later. Kukui and Ash later re-sent out Incineroar and Torracat. Both sides gazed at each other as they walked around one another, before using Darkest Lariat and Flame Charge. Torracat managed to wound Incineroar, then went to use Fire Fang, but got countered by Incineroar's Throat Chop. While Incineroar used Bulk-Up, it struggled to stop Torracat's Fire Blast, before being knocked down by his Flame Charge. As Torracat went to use another Fire Fang, Incineroar grabbed it by its head. Torracat could not escape its hold,and got bashed away by Throat Chop. Since both sides have fought valiantly, both Incineroar and Torracat's abilities activated - Blaze, which powered up their Fire-type moves. Torracat retaliated with Revenge, which dealt a strong blow to Incineroar, knocking it down to its knees. The two sides began to glow with a bright red light, prompting both Kukui and Ash to have them use Inferno Overdrive Z-Moves. As the two Z-Moves collided, both Incineroar and Torracat went into the flames to continue their battle. Torracat's Revenge collided with Incineroar's Throat Chop, dealing a blow to both sides. After the flames subsided, Professor Kukui's Incineroar fell down, defeated.
To mark its defeat during the exhibtion match, the face of Kukui's Incineroar was blackened out at the screen.
- Despite being labeled as a "Heel" Pokémon, the role of Kukui's Incineroar is actually those of Face Wrestlers, much like its trainer, whether disguised as Masked Royal or not.