Julie Makimoto (known as Julie Hayward in Japanese) originated from Bakugan Valley, Australia, later relocating to Bayview. She possesses tanned skin, long pinkish-white hair typically worn in a side ponytail, blue eyes, and favors midriff-baring summer attire year-round. Her wardrobe evolved from a pink outfit with white fingerless gloves and boots (original series) to a dark blue belly shirt and cheerleader uniform (Gundalian Invaders), and finally a black tank top with a pink jacket and white shorts (Mechtanium Surge).

Initially a bubbly, extroverted, and sometimes scatterbrained Subterra brawler partnered with Hammer Gorem, Julie frequently clashed with Runo Misaki due to her admiration for Dan Kuso (affectionately calling him "darling" in Japanese). Her romantic focus shifted to childhood friend Billy Gilbert in the first season, resolving her rivalry with Runo, who became her best friend. Julie proved loyal and empathetic, notably helping Billy break free from Masquerade's control by gifting him a sentimental childhood toy cowboy.

Julie's role expanded beyond battling. In New Vestroia, she advised newer brawlers like Mira Fermin on Subterra strategies despite lacking a Bakugan partner initially, later partnering with Subterra Dyrex. After moving to Bayview alongside Dan and others in Gundalian Invaders, she worked as a waitress and cheerleader while occasionally assisting at Bakugan Interspace, partnered with Subterra Taurus. During Mechtanium Surge, partnered with Subterra Roadem and Adgaran, she transitioned to a non-brawling role as a Bakugan City news reporter. She collaborated with Dan, Shun, Marucho, Mira, and others to establish Bakugan City as a sanctuary. She supported the Battle Brawlers by delivering Battle Suits and handling logistics during conflicts against rogue Mechtogan and Nonet Bakugan threats, including helping prevent Bakugan City's destruction by Mechtavius Destroyer, a crisis averted through the core brawlers' time manipulation.

Her development emphasized growth from a competitive brawler to a strategic supporter, maintaining her optimistic and helpful nature while adapting to evolving responsibilities.