Probation Periods act as Filter
I am often surprised at how much effort some companies put into filtering their candidates at the interview process. Yes, it's important to find out as much as possible and try to get the best person available, but at the end of the day, no IQ or EQ test is infallible, especially for companies in Japan needing bilinguals. There are not many resources that can tell you whether a candidate has the right mix of skills and personality to meet the needs of your firm.
Therefore, it is inevitable that multinationals in Japan use the probation period as part of their employee selection process. Now, I know that this is counter to what a lot of HR people and the Labor Standards officials think, but it is a reality in recruiting.
In Japan, the probation period is a gray area where no one is really sure whether the company has the right to let go of an employee for no reason other than that of incompatibility. Yes, it is a gray area, but experience has taught me that if you warn candidates of your probation policy, most will accept the decision if they are let go.
The law is indeed hazy and if you were to listen to the Labor Standards officials, you'd think that once someone is hired, they're already a full-time employee and very difficult to let go. That is not correct. Providing you stress the probationary nature of the hire and document that fact - then if the employee agrees, you have much better control over the termination process later if needed. Of course, part of this approach is the proper review of a new employee's work progress by their manager and by HR, and a suitable system of warnings and remedial action before termination.
Of course, it's not just the new employee who needs to be informed on how the system works. Current employees also need to understand that the new person is intended to help them become more successful as a team. Therefore, it is in everyone's interest to make sure that the new person is the right person. I try to explain to everyone in my own company not to get too attached to a new employee until they actually pass their probation period, just so that if things don't work out, I don't have a morale problem on my hands.
While trying to get this kind of support, it is EXTREMELY important to give a personal, hands-on explanation as early as possible, and follow up on a frequent basis with comments and questions (and peer reviews) about the new person. This way, no one is surprised if things don't work out, and furthermore it involves them in trying to help the new person become more successful - by encouraging an informal mentor system to develop.
Just for the record, although it may cost a month's separation salary to let a new employee do their whole probation period, I usually do allow new staff the whole 3 months. This lets me evaluate not only their personality and teamwork skills, but also their ability to learn and perform AFTER they have overcome the stress of moving into a new position.