From Bulbapedia, the community-driven Pokémon encyclopedia.
Rocco (Japanese: ロック Rock) is a main character in the Phantom Thief! Pokémon 7 manga. He considers himself a mysterious thief and is Pokémon 7's self-proclaimed rival. He likes to call himself "Rock-sama" in the original version which can be seen as reflecting his proud and stuck-up nature.
Rocco first arrived in town attempting to rid the town of a such a hypocritical mysterious thief as that of Pokémon 7; however, despite their earlier conflict, he grudgingly teams up with his rival to save a Pokémon Thief from Team Galactic. Later he is shown to have a crush on Hiori's sister, Lily. This spurns him into assisting Hiori in her rescue. He refers to her as "Lily-chan", to which Hiori questions.