After swallowing a magic mushroom, Ryôga became a 6-year-old child. To become a 16-year-old boy again, he must swallow a magic mushroom again when it reaches 16 cm. Thanks to Ranma's legendary friendship, Ryôga finds refuge with the Tendô. But as always their friendship does not last long and the latter makes Ranma swallow a magical mushroom of very small size. As a result, the Tendô have to take care of two dirty kids in conflict! Will they succeed in becoming 16-year-old boys again? A matter to follow closely...