4 ways Haki from One Piece is similar to Nen from Hunter x Hunter (and 4 ways they are different)
Haki from One Piece and Nen from Hunter x Hunter are both incredibly well-known shounen anime power systems. Fans love the visual effects of both Haki and Nen and the concepts behind them. Even though they are different power systems from different anime, Haki and Nen have some similarities.
4 traits Haki from One Piece and Nen from Hunter x Hunter have in common
1) They both use a person's innate energy
Haki utilizes a person's spiritual energy. With Haki, users will be able to see a limited distance into the future, create armor to defend against attacks, or overpower an opponent's willpower.
However, Nen allows a person to use their life energy, also known as aura. Using Nen, characters are able to do a variety of things. They can attack, defend, create objects, heal, predict the future, and much more.
2) Each person has a main type they are best at
Both Nen and Haki users have one main type that they excel at. They focus their time and energy on refining and mastering this Nen type and eventually form their Nen abilities around it.
The same goes for Haki as well. Although it is difficult for characters to gain proficiency in the other Nen or Haki types, they are able to use them by training hard.
3) They are both used by only a small population
Both Haki and Nen are used by a relatively small number of people. However, the reasons for why this is are different for both series.
In One Piece, not many people use Haki because they do not realize they have it. Every person in the world can use Haki, but many go their entire lives not knowing it exists.
However, not everyone can use Nen in Hunter x Hunter, and the existence of Nen is controlled. Typically only Hunters are allowed to learn about Nen's existence and train in it. In the Hunter x Hunter universe, it is believed that this would make it easier to maintain social order around the world.
4) They can both run out if used too much
One Piece has shown characters running out of Haki all the time. When they use too much Haki in a fight, they must wait for it to regenerate over time. They will then be able to use it again.
This seems to be the case in Hunter x Hunter as well. When a character runs out of aura, they must rest and wait to recover it. But they are also able to utilize their aura in a way where one attack drains them completely, such as what happened with Netero after he used the Zero Hand.
4 ways the two power systems are completely different
1) Nen is a much more complex power system
Nen is known for being incredibly complex. It is probably the most difficult power system to understand in all of shounen anime. This is due to it being based on a Nen user's creativity and all the associated rules. However, Haki is a simpler power system compared to Nen due to the basic types it has.
2) Nen can remain after the user's death
Post-Mortem Nen is a phenomenon where the user's Nen ability remains after they have died and gets much stronger. This typically occurs when the user holds a strong grudge against someone. After they die, their Nen ability takes on that grudge and looks for the subject of that grudge. A good example of Post-Mortem Nen in action was Terpsichora getting more powerful after Pitou's death.
However, Haki does not remain after the user's death. When the user dies, their Haki disappears and can never be brought back again.
3) Users can create contracts with their Nen
By creating certain contracts, Nen users are able to increase the power of their Nen abilities. Kurapika is a very good example of this in the anime. Kurapika made a contract with his Nen, claiming that he would only use Chain Jail against Phantom Troupe members. This gave him the power boost needed to defeat Uvogin by himself.
Haki users in One Piece do not have the option to create contracts with their Haki. They cannot choose to use their Haki in specific situations in order to get a boost in strength.
4) There are six types of Nen, but only three types of Haki
With Nen, there are six different aura types: Enhancement, Emission, Transmutation, Conjuration, Manipulation, and Specialization. Each of these aura types is different from the others and determines how hard it is for someone to master the others.
There are only three types of Haki in One Piece. Kenbunshoku Haki, Busoshoku Haki, and Haoshoku Haki are the different types. The first type, Kenbunshoku Haki, grants the user precognitive abilities. Busoshoku Haki allows the user to equip an invisible armor. Haoshoku Haki allows the user to overpower another person's will with their own.