Six years ago, a navy colonel had eaten this fruit because of fate. As a result, he not only had the waste ability but also become a dry duck, who cannot enter the sea or swim anymore.
According to the navy, this fruit allows the user to see the strength of people in terms of level as Lv.5 is stronger then Lv.4 or 2.
But the user can only see the level of other party based on his own level. If the difference between strength is too great then he cannot see it. It only shows Lv.???
Apart from it, the user can also see a blood strip line and a blue line above the head of others.
After some experimentation, it was found that red line represents the health of other parties while the blue line represents how much abilities other parties can use and for how long as Haki, Devil Fruits.
If the blue line finishes completely it means other parties can no longer use Haki or Devil Fruit powers.
While Redline finishes represent death.
Apart from it, user strength also can be represented as Level.
But user strength does not match his level, this was a big problem as User Level is Lv.10 but he cannot even defeat an Lv.5
So, it was depicted that user Level does not represent strength but instead serve the purpose of seeing other people levels.
As if User level is Lv.10 then he can see the level of up to 50.
But above it, it shows Lv.???
As Garp, Z, Salazuki shows Lv.???
Navy Colonel who ate this fruit also said that whenever he kills someone, he receives a message that says: " Congratulation! You receive XXXX Exp."
And sometimes " Congratulation! You Level Up! " or
" Congratulation! You receive 5 points! "
According to him, Exp represents his progress of fruit growth as every time Exp. reaches a certain amount he levels up which allow him to see more levels upper than him [ Of higher strength ].
As for points, he said he don't know what they do. So, he ignored them after some time.
The reason his power was termed as waste was due to reasons :
1. Normally Devil Fruits users get some type of power which may increase their body strength like zoan or give him control of some elements like logia or paramecia or some other sort of powers.
But his power is too see other person levels, but even level can not represent about everything as he may be a swordsman or devil fruit user or Haki user or a genius at using techniques like NAVY 6.
2. In One Piece world, there are already ways to judge the strength of other parties as by the value of their Bounty or their Navy Ranks or their fruit power or by their doriki value [ Doriki is a unit of measurement used by CP9 to directly determine the physical power of someone. ]
So his power is not very useful.
3. Normal devil fruit powers can be grown by exercising that power or by enhancing physical strength or training. But, his devil fruit can only grow by killing.
But Navy instead of killing, arrest pirates most of the time.
And killing same Lv. of opponent gives him lest Exp.
But the strength needed to defeat Upper Lv. opponent is what he doesn't have.
4. Devil fruit users become cursed by sea, so they cannot touch sea water anymore or they will lose their power and strength.
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There are many similar waste devil fruits. But this one got so famous because the fruit was waste but the user was a genius, a genius that can only be found in 10 or 100Yrs. So, his fruit didn't give him strength but instead become his weakness. Due to this reason, this fruit becomes well known.
He was very talented in all Navy Six Techniques and train them to their peak which is something very few people can do [ Rob Lucci also did the same. ] {Member of CP9 later CP0}
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