9岁的人类少年莲（宫崎葵 配音）痛失母亲，他拒绝亲戚的照顾，独自跑上熙攘的大街，偏巧遇到了偶然来人间寻找弟子的怪物熊彻（役所广司 配音）。怪物界的宗师（津川雅彦 配音）即将转生为神，接任他位置的人选将在猪王山（山路和弘 配音）和熊彻之间产生，但是没有嫡传弟子让熊彻希望渺茫。借此机缘，莲闯入了怪物世界，他和熊彻之间争吵不断，可是在冲突的过程中似乎又渐渐认同彼此。转眼间莲（染谷将太 饰）已成长为武功高强的落落青年，他无意中回到人间，重拾了失落已久的身份和感情。 　　与此同时，决定宗师的日期一天天临近，谁也没有想到的意外却发生了……The latest feature film from award-winning Japanese director Mamoru Hosoda (Summer Wars, Wolf Children): When Kyuta, a young orphan living on the streets of Shibuya, stumbles into a fantastic world of beasts, he's taken in by Kumatetsu, a gruff, rough-around-the-edges warrior beast who's been searching for the perfect apprentice. Despite their constant bickering, Kyuta and Kumatetsu begin training together and slowly form a bond as surrogate father and son. But when a deep darkness threatens to throw the human and beast worlds into chaos, the strong bond between this unlikely family will be put to ultimate test-a final showdown that will only be won if the two can finally work together using all of their combined strength and courage.