Summary for applying for an apartment in Tokyo
-Have your proof of income ready
-Easiest if you're an employee
-Bring your bank books and any relevant invoices etc.
-Be ready to substantiate your reasons for moving
-Be ready to share relevant contact details
-Be prepared to wait ~4 working days for the application to go through
-Be available. You will likely be called by guarantor companies, management companies/landlords
There are a lot of articles, forum posts etc. on renting apartments in Japan, all of which are pretty easily accessible from Google; however, I thought I'd share my experience on background checks for renting, which I couldn't personally find much information about.
So, I'd found some places on athome.jp that I liked, emailed the estate agent involved, and arranged a meeting. As seems pretty typical, none of the places I'd found were available, but they showed me some other places instead. I found one I liked, and we headed back to the office to start the application.
During the application (which took about an hour) I filled out a couple of forms. You might save a minute or so by knowing your birth date in the Japanese calendar. You'll probably save considerably more time if you're not self-employed. I am self-employed, so I also had to show reasonable proof that I could make the rent. I had 2 months worth of invoices (they would have preferred 3) and my bank book, of which they took copies.
They also wanted to know the reason I was moving to Tokyo. Now, in my head, the reason is that I'm more likely to find a research position in Tokyo than in rural Japan; however, in actuality I'm only in relatively preliminary discussions with one of the professors over here. Nonetheless, I opened my big mouth, assuming any old reason would do. This actually ended up with me having to provide the aforementioned professor's contact details (thankfully the professor is a nice guy, and was willing to help out), and these were not just retained by the estate agent, but passed on to both the guarantor company and the apartment's management company. To try and avoid making myself look like a complete ass from my prospective professor's point of view, I stressed to the estate agent, guarantor company, and management company that unless something firm was decided upon, my main subsistence was from my translation work.
At some point, and I don't recall exactly why, the estate agent took a copy of my PhD certificate. It was probably relevant to something I said.
After making the application on Saturday, I got phone calls from the guarantor company and management company on Monday and Tuesday, respectively. Basically they just went over the contents of the forms I'd filled on Saturday, and concentrated on the weakest part, being the reason for moving, to which I basically said moving to Tokyo will also be helpful for my translation work, but I intend to do research if possible. I think they were also keen to double check my earnings.
On Wednesday, I got the call from the estate agent to say the application had been successful. Just 4 days from applying! I'm pretty thrilled about that: I thought they were going to keep me hanging for at least a week, and I was half-sure they were going to reject it.
On reflection, I'm not sure how useful my case is. I imagine most people will not be self-employed, which will mean they have all the proof of income and reasons necessary to make things as smooth as possible. Also, perhaps having a professor (and a PhD) to vouch for me made a difference? Mine is a pretty unique case, so all I can really offer in advice is to have all your proof of income and be ready to substantiate your reasons for moving. For example, I really should have contacted the professor beforehand.
Still, as far as time scales go, you can probably expect to wait just a few days for the check to go through before you know you'll be able to move in.
Lastly, if possible, I advise using a Japanese-speaking estate agent, I went both the a gaijin-friendly and to a normal estate agent, and found that the normal estate agent tended to have the better deals, or in the very least was more inclined to show them to me. If you have the patience to go to 2 or 3 estate agents, then I would highly advise it.
Oh, and never take flats on the ground floor. Maybe my nose has been over-sensitized by damp, dingy England, but the first-floor apartments I viewed universally smelled of mold. Given that I've lived in a house for the last year, and that the ground floor here is fine, I didn't really believe it, but having actually gone to 3 first-floor rooms and taken a good whiff (as well as inspect the cupboards for mold, and found it in 2 of them: use a torch or the light on your phone and look at the corners of the most difficult to clean part of the cupboard, usually the underside of the lowest shelf to the floor -ignore any strange looks from the estate agent- any fluffy specks that come off when applying pressure with your finger are probably mold), I'm never going to consider a ground-floor room again.