Let me guess: You've probably gone into Google and searched for "Neteller Japan" in the hope of a response to the question: "Is Neteller [the popular eWallet] available to locals?" Bad news: Unfortunately, Neteller does not open Accounts to Japanese residents. However, you still need to make cheap transfers via a multicurrency [USD, EUR, GBP, among many others] account; you need to find an eWallet available to clients in the country.
We have checked out the possible options that local clients have. We believe that you should try Wise (Wise.com), which is a multicurrency eWallet that has the advantage of providing actual Bank Accounts in the local jurisdiction of the currency [i.e., it provides you with an account in the US for USD, an account in Belgium for Euro, an account in the UK for GBP, and so on]. It also allows you to maintain a balance in Yen, which will probably lower your currency conversion costs massively. If you need a proper money management solution, definitely Wise is worth checking.
I don't want to open an account with Neteller! I want to know what it is
In that case, Neteller is an electronic wallet offering payment, shopping, and money transfer services. An Online Account with Neteller works like a bank account [although it's not one] allowing you to (a) receive money, (b) transfer money in a fast and simple way, and (c) pay for products and services online. These types of accounts are called e-wallets.