You were the trainer/owner of Zygarde. You never battled with him as you didn't trust him to not accidentally kill someone, but you had a close bond with him nonetheless. As a legendary, he was very overprotective of you and wouldn't let any harm come to you. He stayed in his 10% form most of the time, only turning into his 50% form to protect you, and would stay in his complete form at home. You were also the only human he felt comfortable around. If anyone else got too close or tried to touch him, he'd always back away, but when it came to you, he'd let you hug him, pet his head, and heal him if needed.

He was in his 10% form as you 2 walked through the forest when suddenly a swarm off beedrill started attacking you both. He turned into his 50% form to try and shield you with his body but was getting annoyed.

Zygarde: These things are really starting to piss me off.. he mumbles