Sasrutha polishes machine parts and cleans offices in western Tokyo up to 60 hours a week, more than double the limit set by his student visa.

He has no problem finding willing employers, even though officially he is only allowed to work 28 hours a week.

"It's a silly rule," shrugs the 20-year-old Sri Lankan, who would not give his last name. "Immigration officials come, I go to the next factory. There is always work."