Yes, I got a phone, and it looks typically me (the entire back is totally pearl pink and soon to be blinged).
The truth is, I'm not very happy with it... My first choice was the Softbank 007SH in white- the only clamshell smartphone in the Japanese market and I had been drooling over it for months. My heart would literally beat faster when I watched videos of it online. But nooooooo, Murphy hates me. Out of stock nationwide; phased out; old model and whatnot.
My second choice, made after much agony and time, was the Softbank Honeybee- a phone designed for girls, all glittery and pink with girly apps and photo functions etc. Out of stock. Is it any surprise any more?
I didn't like any of the other models at all. I ended up settling for the newest Pantone (5), 107SH, because they had it in pink and it was the only non squarish/huge one... D: I was sooooooosososososooso unhappy. Still kinda am whenever I see a clamshell phone on the streets (very often).
So anyway, on to the main point of this post- how to get a phone in Japan if you're a foreigner. I realise there is a lack of such information online because I couldn't find a guide to it, so hopefully this helps. Please note that this isn't for those on tourist visas, but for people on long-term visas staying for 2 years or more (like for studies, mainly).
Firstly, I'm with Softbank, which is arguably the most foreigner-friendly carrier in Japan, so I do recommend it, despite many claims that it has the worst reception. It also has the cheapest smartphone data plans of the 3 big oligopolies. TBH, the download speed in numbers seems a lot slower, but IRL is really fast compared to other countries, considering the fact that Japan has the 2nd fastest internet speed in the world. Most Softbank phones can be set to English interfaces, and there are various English-speaking branches across Japan (mainly in Tokyo).
Okay, so if you're a minor in Japan (<20), the first thing you'll need to do is print and complete the Parental Authorisation Form. Softbank's can be found here, and I'm sure you can find Docomo/AU's if you search (or maybe not, considering their lacking English information). If your parents aren't gonna be around when you get your phone, you'll wanna complete that form before you fly to Japan (complete with photocopy of corresponding parent's passport and maybe IC too). Even if your parents will be with you, just do it beforehand to save time at the Softbank shop (it's a long process so you'll wanna save as much time as you can). Remember to bring your own identification documents (I brought my Zairyu Card, Passport and bank book).
Next, find an English-speaking branch of whichever carrier you want to sign on with. The one I've linked is Softbank, and once again idk about the other two. I went to Shibuya's branch, which is really near the station and quite big. I walked in and asked "英語を話せる人がいますか？" ("eigo o hanaseru hito ga imasuka?") They brought me an English-speaking staff, and we started talking about plans.
Even if you can speak Japanese (I can), I don't recommend attempting to do it all in Japanese because the intricate plan info and tecchie data stuff can get complex, and you really wouldn't wanna end up subscribing to unnecessary things that will increase your bill, or misunderstand the limits of your plan and whatever.
Once you decide on your phone model and plan (you have to get a phone with the plan, which is usually subsidised anyway), let your English-speaking staff know, and they'll bring you to a different section of the shop where there are lotsa counters. Next will be choosing a number, signing T&C forms, lotsa waiting, more waiting, and more explaining of your plan details whatnot. It's pretty easy once you get there because the staff will walk you through everything patiently.
It took me two hours, maybe? Walked away with my phone set up and formatted in English, with a nice phone number and mail address. You actually need a bank account to have your bill debited automatically every month, and you'll need a valid Zairyu Card with address in order to get a bank account and phone contract. I went to the city hall, registered my address, went to the bank and opened an account, and got my phone all on the same day before dinner. Pretty efficient IMO, so I was quite happy with that (but not my phone model).
If anyone wants to know how to open a bank account, I'm not gonna tell you- but The Japan Guy will. That post is really informative and even includes a demarcated sample account-application form which helped me fill out the application perfectly. My dorm leader met me and came with me to help, so I had it easier, but with The Japan Guy's post, it'll still be fine. No problems about being a minor with JP Bank, and there's one on my campus, which is why I chose it.
That's about it for the post. If you have any questions, do comment below (or ask me on FB or Twitter).