The dozens of young Chinese engineers looked nervous, but eager, as they presented their work in English during a hack-athon in September at the high-rise Roppongi Hills complex in Tokyo.

But while the event hosted by Mercari Inc., maker of a popular flea market app, appeared to be a mere tech competition, it was actually far more.

The hack-athon was, in reality, a part of a four-day, all-expenses-paid recruitment visit to Japan by top-notch Chinese engineering students. It featured 33 participants — all college students from China's most prestigious schools, including Tsinghua and Peking universities.