You can buy in through any major cryptocurrency. Assuming you can get past the Know Your Customer checks, the actual purchase is done through the Blocktrades web site. You can choose which crypto to send them, and then they send you back the equivalent amount of MIT tokens. You do need an Ethereum account to store the MIT.
As a good way to get started in crypto, I recommend opening a trading account on https://www.kraken.com . Kraken is a reliable cryptocurrency exchange that can connect directly to a Japanese bank account for withdrawals in yen. And yen deposits can be done by furikomi from regular Japanese ATMs. Whenever you have a spare ichiman lying around, zap it to Kraken and buy a little crypto. It's fine to keep a bit stored on the exchange, but once you've built up a sizeable amount it would be good to move it off exchange into a wallet account that you control the private keys to. I also like the Poloniex exchange; it supports a wider variety of cryptocurrencies than Kraken and is easier to use. But Kraken can't be beat as a Japan friendly onboarding ramp.
I too had very little money when I first got started. I wouldn't recommend it, but I used a cash advance from my US credit cards to buy my first couple Bitcoin. I finally repaid that advance just a couple months ago from some of my profits, and boy did that feel good.
I guess you've got to get started somewhere, but, yeah, a cash advance sounds a little risky. I'll sign up for a Kraken account and see if I can't find a little extra money lying around. Thanks for the advice!
You're welcome. Good luck, hope it works out!