As a Rockruff, his first appearance was in A Ten Carat Capture!, where he was met the group while they were visiting Ten Carat Hill. He happily played with the group's Pokémon and took a particular shine to Lewis. Rockruff later assisted Lewis in battling some Team Skull grunts who were causing trouble in the cave. After dispatching the grunts, Lewis asked Rockruff to come along with him. Nodding in agreement, Rockruff allowed Lewis to catch him.
Rockruff was Lewis' second Pokémon in his Grand Trial battle with Hala in The Call of Tapu Koko! He battled against Hala's Makuhita and defeated it with Rock Slide. Rockruff then faced off against Hala's final Pokémon - Crabrawler. Despite putting up a good fight, Rockruff was unable to withstand Crabrawler's punches and was defeated.
Rockruff was sent out by Lewis to battle Hau's newly-evolved Pikachu in A High-Voltage Rivalry!, although the result of the battle was not seen.
Rockruff was Lewis' first Pokémon used in his Brooklet Hill trial. It struck the Totem Wishiwashi with Rock Slide and followed up with a Tackle. However, Wishiwashi's damage was quickly healed by its Alomomola allies and Rockruff was defeated by Aqua Tail.
In Conclusion to a Royal Bout!, Rockruff was used by Lewis in the finals of the Battle Royal Tournament. It faced off against Mars' Chimchar, Mallow's Steenee and the Masked Royal's Machoke. Despite having a type disadvantage against all three, Rockruff managed to gain the upper hand after Chimchar defeated Steenee. After tricking Machoke into hitting Chimchar with Dynamic Punch, confusing it, Rockruff was able to beat Chimchar with Rock Slide. It then battled one-on-one with Machoke and eventually defeated it using Breakneck Blitz.
In the next episode, Lewis used Rockruff as his second Pokémon in his battle against Kiawe. Rockruff faced off against Kiawe's Fletchinder and managed to withstand its Flame Charge before defeating the Ember Pokémon with Rock Slide.
In Rockruff and the Moonlit Future!, the group began to notice Rockruff acting strangely, becoming more aggressive in battle and howling at the sunset. Later that night, Rockruff left the group and sat atop a rocky outcrop to howl at the moon. Lewis, having followed Rockruff, saw this and witnessed Rockruff evolve into a Midnight Form Lycanroc. The next morning, Lewis decided to test Lycanroc's new power with a battle against Mars' Rhydon. During the battle, Lycanroc demonstrated that it had learned Brick Break, however Lycanroc refused to obey Lewis' commands, having decided that Lewis wasn't worthy of being his Trainer. Despite his power, Lycanroc was defeated by Rhydon's Mega Punch.
Lycanroc would continue to disobey Lewis until A Rhythmic Trial Battle!, where it faced off against a Totem Salazzle. Realising that Salazzle was an extremely powerful opponent, Lycanroc agreed to work with Lewis to defeat it - seeing it as a "common enemy" for the two. However, after defeating Salazzle, Lycanroc went straight back to disobeying Lewis' commands.
In The Edge of Unity!, Lewis was challenged by Yarris, a Trainer with a powerful Gigalith who went around challenging powerful Rock-type Pokémon. Lewis sent out Lycanroc to battle, who was initially against battling until it was struck by Gigalith's Flash Cannon. Recognising Gigalith's power, Lycanroc once again agreed to fight alongside Lewis. Despite this arrangement, Lycanroc was still defeated by Gigalith. Yarris informed Lewis that although Lycanroc obeyed his orders in this battle, it was for his own gain and reveals that Lycanroc doesn't fully trust his Trainer. Determined to regain Lycanroc's trust, Lewis took it into the mountains to train. During their training, Lewis saved Lycanroc from a fall, reminding Lycanroc of everything Lewis did for it while it was a Rockruff. His trust in Lewis restored, Lycanroc agreed to work together with Lewis from that point on. Lewis and Lycanroc then challenged Yarris to a rematch. Due to them being in sync once more, Lycanroc was able to put up more of a fight against Gigalith, eventually defeating it with his newly-learned Stone Edge.
In Clash Atop Memorial Hill!, Lycanroc was used to battle several Team Skull grunts who had stolen jewels from Konikoni City, catching the attention of the Akala Island Kahuna, Olivia, in the process. Olivia recommended that Lewis use Lycanroc in their upcoming Grand Trial, to which both Lewis and Lycanroc agreed.
In the following episode, Lewis sent out Lycanroc as his second Pokémon in his Grand Trial with Olivia. It took on Olivia's Nosepass, who had previously defeated Vulpix. Lycanroc quickly defeated Nosepass and was recalled by Lewis to save for later. Lycanroc was later sent out as his final Pokémon, facing off against Olivia's Midday Form Lycanroc. The two Lycanroc proved evenly matched, although Olivia's Lycanroc's superior battling experience allowed it to gain the upper hand. Olivia's Lycanroc launched a Continental Crush, but Lewis' Lycanroc was able to reduce the damage by breaking apart the move using Brick Break. After this, Lewis took advantage of Olivia's Lycanroc's tiredness and had Lycanroc attack with Stone Edge, sending Olivia's Lycanroc flying into the air. Lycanroc then finished off its Midday counterpart with a powerful Brick Break, earning Lewis the Akala stamp and a Rockium Z.
Lycanroc was sent out to help fight Novu's Rusted Pokémon in The Age of Rust! Here, he performed Continental Crush for the first time to take out several Rusted Pokémon.
Lewis used Lycanroc to battle Molayne's Alolan Sandslash in Trial for the Trial!, where he easily defeated the Mouse Pokémon with Brick Break.
In the following episode, Lewis used Lycanroc to fight the Totem Vikavolt. Lycanroc took advantage of Vikavolt's lowered speed from battling Vulpix and dealt a few blows with Stone Edge and Rock Slide, although he was caught off guard by a powerful Energy Ball and knocked out.
Lycanroc was used by Lewis to battle a wild Turtonator in Setting the Trap! Hoping to use Lycanroc's type advantage to defeat Turtonator, Lewis had it use Rock Slide to try and block Turtonator's incoming attacks. However, Turtonator's Dragon Pulse was able to smash through the rocks and hit Lycanroc, who followed up with Crunch. Turtonator then used Shell Trap to deal a large amount of damage to Lycanroc. Unfazed, Lycanroc proceeded to attack with Brick Break. Turtonator then unleashed a powerful Payback move, which knocked Lycanroc out.
In Lycanroc Goes Forth!, Lycanroc was sent out to battle a 10% Forme Zygarde, who believed the group to be upsetting the balance of Alola. Lycanroc fought evenly against Zygarde and dealt a huge amount of damage using All-Out Pummeling. Despite this, Zygarde remained standing and knocked Lycanroc to the ground with Dragon Pulse and then used Thousand Arrows, although it diverted the attack after seeing Lewis rush in to protect Lycanroc. Witnessing the bond between Lewis and Lycanroc, Zygarde stopped the battle and acknowledged Lycanroc as a worthy opponent before leaving. With Zygarde gone, Olivia approaches Lewis and offers to train Lycanroc, having become impressed with its strength. Lewis leaves the decision up to Lycanroc, who agrees to go with Olivia, bidding an emotional farewell to Lewis.
As a Rockruff, Lycanroc was a very happy and friendly Pokémon. He quickly became friends with Lewis, his friends and their Pokémon after only knowing them for a short period. He demonstrated his loyalty to Lewis by helping him battle some Team Skull grunts, despite Lewis not being his Trainer at that point.
Rockruff remained extremely loyal to Lewis, always trying his hardest in battle and refusing to give up despite being up against far stronger opponents, making his personality very similar to Lewis'.
Upon evolving, Lycanroc lost his loyalty to Lewis and instead began looking down on him as unworthy of his power, becoming quite self-centred. Despite this animosity, Lycanroc agreed to battle alongside Lewis only against "common enemies" he deemed were too powerful to fight alone (namely Totem Salazzle and Gigalith), although he did not truly trust Lewis in battle, still maintaining his belief that Lewis wasn't worthy. However, after being saved by Lewis, Lycanroc began to trust him more and agreed to battle with him as equals, finally letting go of his self-absorbed personality traits. Since this event, Lycanroc has remained a very serious Pokémon, rarely showing emotion beyond the odd rough smile during battle, although it continues to obey Lewis.
Lycanroc is shown to have a high respect for those he deems powerful, such as Olivia and her Lycanroc, Zygarde and Lewis himself eventually. He is shown to enjoy the thrill of battling these powerful opponents and fights with a strong code of honour.