The Motoda couple took in their brother's son, Makoto, for certain reasons. However, Makoto's younger brother, Tetsuya, grew jealous of his outstanding personality and became resentful, shutting himself off emotionally. Concerned about Tetsuya, Natsuki gradually grew closer to Makoto, drawn to his warmth. But once Makoto discovered their relationship, he suddenly changed his attitude, hurling cold words at Natsuki and eventually resorting to physical assault. Upon learning this, Tetsuya flew into a rage and attacked Makoto. Thus began the days of both sons tormenting and training Natsuki as their plaything.