Manga artist Kamentotsu didn't expect much when he uploaded a four-panel strip about an anthropomorphic bear who runs a cake shop to his Twitter account three years ago.

But the first installment of "Koguma's Cake Shop," drawn as consolation for a tired friend, attracted tens of thousands of likes. Within a week, 40 companies had approached him with offers.

"Publishing company editors have gone from bringing up manga artists, like they are farming, to hunting for them," said Kamentotsu, who goes by his pen name and wears a mask in media appearances.