Trading Deadline in Japan?

Yes and no.

There is a deadline, some time around the All Star Break, after which teams can no longer make trades. The signing of new foreign players extends a little longer, I think.

However, trades themselves are nothing like in the Major Leagues. Some teams (Giants) deal players away as a punishment rather than to build a stronger team. Most in-season trades are border-line ichi-gun/ni-gun players that don't really have much of a future on their current teams.

2006 In-Season Trades (through June 24, 2006):

3/24 Kazuki Fukuchi (Hiroshima to Seibu)
3/24 Hayato Aoki (Seibu to Hiroshima)
3/27 Hideki Okajima (Giants to Nippon Ham)
3/27 Kazunari Sanematsu (Nippon Ham to Giants)
3/27 Shigeyuki Furuki (Nippon Ham to Giants)
4/28 Ryutaro Doi (Yokohama to Lotte)
4/28 Ryusuke Minami (Yokohama to Lotte)
4/28 Shigetoshi Yamakita (Lotte to Yokohama)
5/08 Akira Matsumomto (Softbank to Rakuten)
5/08 Hidemitsu Saitoh (Rakuten to Softbank)
5/25 Takashi Kawai (Lotte to Rakuten)
5/25 Ken Shinzato (Rakuten to Lotte)
6/06 Shinsuke Yamada (Giants to Hiroshima)
6/06 Takuya Kimura (Hiroshima to Giants)
6/19 Hiroshi Narahara (Nippon Ham to Chunichi)
6/22 Katsuhiko Saka (Rakuten to Hanshin)
6/22 Rui Makino (Hanshin to Rakuten)

As you can see, Rakuten has been the busiest in terms of trades. And I'll confess that these trades have been most likely for the reasons that MLB teams trade, to improve the team. But Okajima's was punishment for not being the closer the Giants wanted him to be.

I totally missed the Kimura/Yamada trade. A veteran player for a career ni-guner? Does anyone know what that was about? To allow Kimura to retire as a Giant? (That's another fairly frequent reason for trades, to allow some veteran the prestige of finishing his career as a Giant.)

I think the Kimura trade was because of Kyojin's various injuries. Also, Kosaka and Nishi were around the Mendoza line with their bats and Kimura can play a number of positions. He probably wasn't in Brown's future plans, since I'm sure Brown wants to go younger with the Carp. I don't think Kimura got a single call up with the Carp this year.