高校生の十代、神ヶ崎裕也は、隣の巨乳の友人に誘われずに立ち寄ることもない限り、まったく平凡な生活を送っている。High-school teen Yuya Kamigasaki lives a perfectly average life, when he isn't dropping in uninvited on his big-breasted friend next door. One day, a magical circle appears in his room, revealing Angelia, a princess from another world who offers to "reincarnate" him into the greatest hero that ever lived. This would-be hero's life is about to get a lot less boring and a whole lot more dangerous.