Hey guys there are many things which I would like to know about One Piece and I would really appreciate if you could take your time and at least answer 1-2 of my questions.
1. Please explain the three types of Haki to me (especially the third, "special" one)/ and Haki in general
2. In which episode does the Haki first "appear"?
3. What kind of devil fruit does Ace have? Paramecia?
4. Can you explain what Logia devil fruit exactly does?
5. When does this Brooks guy come to the Straw Hats? (which ep)
Okay guys, that's all for now. I hope that you can give me some answers. :'D
Answering these questions might spoil you if you haven't really read or watched one piece you know?
1. There are 3 types of haki. Observation, Armanent, and conquering haki. Observation allows you to predict the moves your opponent will use next. It has other uses such as being able to count how many people/animals are in a certain area, determine peoples feelings, and determine others strength.
Armanent haki allows a person to use haki as a weapon or shield. It can be infused into parts of ones body to increase the strength of their attacks, when armanent haki is in use it also acts like a shield. Generally without having overwhelming power if a person is using decent armanent haki and their opponent isn't, they can't be hurt. Armanent haki also allows a person to essentially nullify devil fruit abilities. It allows people to hit logia users as well as hurt people that can't be hurt if they were punched normally, like luffy. Conquerors haki uses ones will in order to knock other people or animals out who's will is not strong enough to counter the haki. Only select people have this, usually people who have made large names for themselves in the new world will have this. haki.
2. We see Haki in the very first chapter of one piece and episode 4 of the anime. You do not know that it is called haki at the time, and don't learn that it is called haki for a long time.
3. He has a logia type devil fruit, called the mera mera no mi. It is flame logia.
4. Logia devil fruits are very prized because they make the users practically invincible. The only things that can essentially hurt them are other devil fruit that are capable of bypassing the logia's ability somehow, armanent haki, or being underwater. Most people don't know haki until the new world and there aren't many devil fruit to counter logia. So really they are pretty invincible as long as they avoid water. The logia devil fruit gives the user the ability to turn into what the fruits name implies, and in doing so allows them to not take damage like a normal person and makes them essentially invincible.
5. Um shit. I watched the episodes quite a while back. I think he joins the crew around episode 380, but by then we have already known about him for like 30 or 40 episodes prior.
I really suggest looking at the one piece wiki for more in depth answers, especially for questions 1 and 4. Just search haki and logia on the one piece wiki and you should be able to find what you are looking for. As for question 5 the one piece wiki also has an episode guide which can help you out.