After stumbling upon a secret laboratory, Yuuta Tomonaga made a habit of sneaking inside after hours to spend time with his new friend: Deckerd, a giant mecha being developed for the Japanese Police. Over the past six months, Yuuta has taught Deckerd concepts which he was never meant to understand; things like joy, anger, sadness, and having a "heart". But now Deckerd is ready for Police service and his reprogramming will in all likelihood obliterate this knowledge...