Ash's Rockruff initially resided at Professor Kukui's home on Melemele Island. It became friends with Ash and Pikachu when it greeted them by nuzzling the rocks on its neck against them. It also enjoys eating Alola Plate, the traditional home cuisine in the Alola region.

At night, it would leave the professors home to go train at Scratchmark Hill with other Pokémon. Ash and the Professor stayed out of sight as they wanted to see where Rockruff was going when they were away from the home. After training with Rockruff for the dojo battle, Professor Kukui suggested that Ash Ketchum get Rockruff because he was the one that it trusts the most because he helped it master Rock Throw and win the battle against Magmar. Ash took out his Poké Ball and caught Rockruff.

Ash's Lycanroc (Dusk Form) is the evolved form of Ash's Rockruff. It evolved on Akala Island at the Ruins of Life at dusk. A rare natural phenomenon that occurs at sunset and sunrise called a Green Flash occurred and triggered the evolving process. It evolved into a surprise form of Lugarugan that aren't in any books or zukan.