Belly!

Johan: "I'm fine with that, but why does the Devil Fruit appear as part of the system?"

System: (During the transmigration, there were some inconveniences in transferring your soul to this body, so we need to synchronize you with this world... You won't be able to consume a Devil Fruit; the only way to 'obtain' its powers will be by unlocking them through the system.)

Johan: "... But that's garbage!!! Although I prefer garbage over nothing."

Johan: "System, tell me how I can increase my powers. Also, is there anything important I should know about my limitations?"

System: (Certainly, just like with a Devil Fruit, the only way to become stronger is through the system, by increasing attributes or unlocking others. Any training you do on your own won't have any impact on your abilities, whether physical or mental.)

Johan: "Is this system really helping me or preventing my progress?"

Johan: "Anyway. System... explain the procedure for increasing attributes."

System: (Alright. As the name suggests, the 'Bounty Hunter System' involves the collection of materials, in this case... 'Bellys,' which is the formal exchange currency in this world. To increase attributes, you just need to deposit money into the 'Three-dimensional Space,' and it will automatically convert into talent points.

The exchange rate is as follows: $3,000,000 for each point assigned to 'Physical' attributes, which include Strength, Agility, Stamina, and Vitality. $30,000,000 for each point assigned to 'Skills' or 'Techniques,' which include Rokushiki, Fencing, Melee Combat, and Haki.)

Johan: "Hmmmm, this totals to $1,188,000,000 in Belly for physical attributes and $3,000,000,000 for skill attributes, practically the reward of a Yonkou."

System: (These are just basic attributes; when you complete some attributes, you'll naturally be able to unlock others or simply purchase new items in the store.

Here are the available items:

*Dragon Ball: Senzu Bean $50,000,000, "Heals any illness and restores energy by 50%, the host can only have 3 in their inventory."

*Seven Deadly Sins: LostVayne Sword $200,000,000, "Allows the creation of up to 4 clones of the user, splitting power equally, and reflects weaker attacks back to the host."

*Naruto: Kubikiribōchō Sword $250,000,000, "This item can regenerate by absorbing the blood of victims, thus repairing itself automatically."

*Various: $100 "Knife, Bread, Shirt..."

*Berserk: Berserker Armor $400,000,000, "This armor provides a significant increase in all abilities, increases physical resistance while sacrificing internal damage, can only be used once per day. Items from other worlds will be properly rebalanced for this universe to avoid inconveniences.)

Johan: "There are more items than I expected. And what about the Marines or any external pirate forces that don't have bounties?"

System: (They will be classified based on their rank, taking into account the main military ranks:

Marine Captain: $20,000,000.

Commodore: $50,000,000.

Rear Admiral: $100,000,000.

Vice Admiral: $250,000,000.

Admiral: $1,000,000,000.

In these cases, Belly will automatically move to your inventory only by killing the target.)

Johan: "Well, that seems fair. In theory, it's quite simple to obtain Belly, but considering that I'm now just an ordinary human, it will be somewhat challenging."

Johan: "System, if someone obtains Belly as my subordinate or in some way other than their own methods, will the exchange value be the same?"

System: (In the case of obtaining Belly through methods external to the host, the value of the Belly obtained will be reduced by 90% to maintain balance.)

Johan: "Ahh..., do you have the audacity to minimize my actions to maintain balance, but you don't have the power to enable my training? You're cheekier than I am. Bahahahaha."

System: (Entering suspension mode, I will activate again when you have completed all attributes. Only the "Status" function will be available.)

Johan: "Useless system."