Can I use the same English (US) Yahoo Search (Overture) account to advertise to Japanese market ?
Although you have a US account, you must create a separate Japanese account. To open an account, you have to sign up from their Japanese registration form. You can switch to English from the middle of the signup process. Even if you switch to English, any price information will remain as Yen. However, the charge will be automatically converted from Yen to US dollars.