However, Mousse's experiment had not ended. It had merely shifted into a phase of tracking and observation.
First, he began urging his sister, whose physical qualities had improved remarkably, to train her body. Yet he discovered that the results were unexpectedly poor, even worse than when she had often slacked off before eating the Devil Fruit.
Mousse thus inferred that the boosts gained from eating a Devil Fruit were more like permanent buffs. They did not add to one's current foundation or truly improve one's innate talent.
Considering that the main value of Devil Fruits lay in their special abilities, Mousse could understand this, though he still felt somewhat disappointed.
Second, he deliberately selected a test subject who had already passed the age of growth and had little potential left, then prevented him from undergoing any intense training. Mousse discovered that this Devil Fruit user's vitality and mental strength were still continuously increasing.
Thus, he reached an extremely important conclusion: "The boost is not a one-time effect gained at the moment one eats a Devil Fruit. It is a fluctuating effect based on the degree of Devil Fruit development."
Comparing that conclusion with a piece of common knowledge Katakuri had mentioned before, Mousse finally reached his ultimate conclusion:
*"I remember Second Brother saying that someone with a body that is too weak cannot develop their Devil Fruit ability to its limit. In other words, the upper limit of Fruit development is linked to one's basic abilities. Then is the lower limit—or rather, the starting point of development—also linked to that? When Luffy first ate the Rubber-Rubber Fruit, it showed no value at all because he was only a few years old and far too weak. But Blackbeard could collapse Marineford with the Tremor-Tremor Fruit as soon as he obtained it