--Long and Drawn Out Process-
I applied to Rakuten through the Boston Career Forum site.
Step 1) Entry/Web Tests
The first thing I did was submit an entry sheet. I guess they liked me, so they prompted me to take a series of web tests.
Test 1- This test was mainly based on English reading comprehension. You read paragraphs, and answer logic questions based on what you read. There wasn't possibly enough time to answer all the questions accurately in the given time limit, so do your best to power through it.
Test 2- This one was full of short algebraic calculations. Nothing too hard. There were mostly a series of linear equations, with a few exponentials sprinkled in. I would recommend having a calculator handy, because you will also be dealing with fractions and decimals. Again, it was not humanly possibly to finish all the questions while adhering to the time limit.
Test 3- This test was fill of logical symbol problems. At first I had no idea what it wanted me to do, but after staring at the example question I caught on. I would say this was the hardest one, but I think anyone with enough common sense could get a portion of the questions right
Test 4- A Personality test. If you have filled out other applications online, you'll know which answers to pick.
All of these tests besides test 4 had an insanely short time limit. I don't know how they grade these things, so just go with it.
Step 2) Interviews/Resume Submission
If you passed step 1, they will schedule you for Skype interviews and ask you to fill out both an English and Japanese version of a Rakuten Resume Template. The resume is in the style of a 履歴書, so you have to write a 自己PR and 志望動機 that is tailored to Rakuten.
The Skype interview felt like a standard interview. A talking head will ask you "Why Rakuten?", "What can you bring to us?", "what did you focus on in College?", etc... They will also ask you "why Japan?". In the middle of the interview, your talking head will start engaging you in Japanese, so make sure you can hold your ground.
Also, know about the Rakuten Shugi and how you identify with it.
Step 3) 2nd Interview and Essay
If you made a good impression, they will invite you for a 2nd interview. Mine happened to be at the Boston Career Forum. They pretty much ask you the same questions, except more of the interview will be in Japanese.
Essay- They will ask you to write a short essay about Rakuten Business' principles before your final interview. Just do it.
Step 4) Final Interview
Mine was surprisingly relaxed. I hit it off with the interviewer and we talked about our mutual hobby.
It finished in 10 minutes
Step 5) Post Interview Dinner
I guess this only applies to people at the Boston Career Forum, but if you made it to the final round, Rakuten will give you invitation to the elusive BCF Dinner Party. They will be drinking. After a long day at the Boston Career Forum, you will be exhausted, but don't get drunk. One drink should suffice. Put on your best face and chat it up with the Rakuten Execs. Smile, laugh, repeat.
Step 6) Final Interview 2?
After you go back to wherever you live, someone from Rakuten will schedule you for a Skyper interview. Be sure to wear your suit. They will probably extend you an offer.
If you follow these steps you will probably get a 内定 from the company.
My one piece of advice is buying 面接対策 book from some Japanese bookstore (Maybe even from Rakuten Ichiba? ;] ) to brush up your Japanese interview skills and manners.