I live in Japan and work at a small Japanese company. In Japan, you must be enroled in either the national pension and health insurance schemes or the employer equivalent known as “social insurance” (pension and health insurance combined). Basically, in businesses with 100 or fewer employees, if you work less than thirty hours a week, your employer is not obligated to enrol you in the company social insurance plan; it's optional on their part. This means you are responsible for enroling in the national schemes and for paying the entirety of your monthly national pension and health insurance premiums. However, if you work thirty hours or more a week, regardless of how many employees, your employer must enrol you in the employer social insurance plan in which they pay half your pension and health insurance premiums. These company pension and health insurance schemes usually have much better benefits and protections than those provided under the national schemes.
One of my coworkers, who works just a few hours shy of thirty “official” hours a week, but who puts in well over thirty hours a week, recently asked to be put on the employer social insurance plan. According to management, she doesn't “qualify” because her official work hours are less than thirty. My coworker pointed out that she regularly works over over thirty hours a week despite not being paid for the extra hours. Management told her they consider the unpaid work to be a necessary “part of the job”. Moreover, they insisted that because her official work hours were less than thirty hours a week, they “couldn't” enrol her according to the labour laws. This is a blatant lie, however, which I myself have clarified with them in the past after a visit to the labour bureau and the pension bureau. They are not obligated to enrol her, but they can if they so choose.
After a bit of back and forth, management proposed a compromise. They would increase her “official” hours by a few more per week by assigning her extra duties (not just in name only), so she would “qualify” for the company social insurance. Despite all the unpaid work she already does in her free time, she considered their offer. She thought she would at least get a slight pay raise to compensate her for the extra hours bumping her up to thirty “official” hours.
Here's the kicker; when she asked how much more she would be paid for the extra hours of work they would assign her, the company told her she wouldn't be paid for them because she is “already paid enough.”