One of the year¡¯s most spectacular startup payoffs isn¡¯t in Silicon Valley or China, it¡¯s in Japan.

Mercari Inc.¡¯s $3.7 billion coming-out party will deliver a 149-times return to early investor United Inc., which engineered a ?300 million ($2.7 million) round in the flea-market app in 2013. That stake will be worth at least ?45 billion when Mercari goes public on Tuesday, a major windfall that may galvanize the No. 3 economy¡¯s stunted startup scene.

¡°The environment is right to see several more unicorns appear over the coming decade,¡± said Yozo Kaneko, president of the Tokyo-listed investment and internet services firm. ¡°But the real consequence is that we¡¯ll see more experienced entrepreneurs come out of those unicorns, and they¡¯re the ones who could have a really big impact on the entire ecosystem.¡±