In sci-fi movies, it's common to see a character having spontaneous conversations with robots and humanoids, like C-3PO of "Star Wars" fame.

In reality, technology hasn't reached that level yet. But big-name Internet firms like Apple, Google, Amazon and Microsoft are inching closer, brushing up voice assistant functions and installing them in their products.

Seeing huge potential for the future, Japanese companies have also been developing the technology. NTT Docomo Inc. and Yahoo Japan Corp., the top two companies competing in this field, are providing voice-controlled functions for smartphones that can conduct online searches, for instance, and are incorporating the technology into other products like toys.