Gareki no Oh

Citro's an all-too-human android boy who lives with his "grandfather," an old mechanic, and Corona, the mechanic's granddaughter. When warring factions battle it out at his home, a powerful device implants itself in Citro, making him both more powerful and the target of evil forces. Tragedy propels Citro and Corona on a quest, accompanied by their new ally Tera, the broomstick-flying, techno-witch.

From:animenewsnetwork.com