I've seen the movie too (great, by the way) and I also thought of Murakami...
Here are the names of all japanese characters which appear in the movie:
Yasujiro Wataya *
Chieko
Mitsu
Kumiko *
Kenji Mamiya *
Hamano
Haruki *
Takeshi
Kazuma
* there's a connection to Murakami I know (absolutely WUBC)