Ryo Takatsuki is a typical Japanese high school student, whose seemingly nondescript way of life started to unravel with the arrival of Hayato Shingu and Takeshi Tomoe, the new transfer students with a history of disciplinary problems. An unexpected chain of events that followed would change the life of Ryo and those around him, from his childhood friend Katsumi to the brash Hayato and the enigmatic Takeshi, who may yet turn out to be friends or foes. With his new found comrades, Ryo sets out to discover the secret of the mysterious A.R.M.S., which would reveal an unexpected destiny for each of them… 凉过着普通的高中生活,班上新来的转学生隼人却认定他是杀父仇人,证据是他身上装有“神臂”!同时一神秘组织“艾格里”也在捉拿他。为了救被隼人捉作人质的青梅竹马的朋友胜美,凉被迫与隼人打斗,两人却同时遭到艾格里的追杀,凉发现自己的右手在战斗中变成了厉害的武器!消除误会的两人成功逃脱后,凉得知隼人的家人朋友均在10年前被艾格里所杀,两人身上均装有ARMS,而这正是艾格里想要抢夺的东西。凉和隼人发现新来的转学生武士也拥有ARMS,而艾格里的天才儿童——双胞胎阿尔与杰夫却以学校作战场,欲置三人于死地