Jesse is Musashi: Jessebella is Musa-pyon, Jessadia is Pretty Musalin, Jessilina is Candy Musalina
James is Koujiro
Professor Oak is Professor Okkido
Delia Ketchum is Hanako
Ash Ketchum is Satoshi
Misty is Kasumi
Gary Oak is Shigeru Okkido
Brock is Takeshi
Tracy Sketchit is Kenji
May is Haruka
Max is Masato
Steven Stone is Daigo Tsuwabuki
Drew is Shu
Robert is Robert
Harley is Harley
Solidad is Saori
Dawn is Hikari
Paul is Shinji
Kenny is Kengo
Reggie is Reiji
Wallace is Mikuri
To fins other names use bulbapedia.bulbagarden.net/ type in the character and their profile will tell you their Japanese names.
Chat with our AI personalities
By main characters, I think you mean the player characters. If so, yes, they have names. The boy is named Hilbert, and the girl is named Hilda. Their Japanese names are similar as well. The boy's is Touya, and the girl's is Touko.
YOU CAN'T, you have to get the game in Tokyo/Japan in order to make the words on pokemon heartgold be japaneze. If you get it in a English state, it will be English!
they are dawn and lucas
Pokemon is Japanese
It is allowed to be up to 12 characters long max and 6 characters max in Japanese and Korean. If you like to have a long name, you'll have to shorten the name or do not add a space, numbers, or special characters.