I'm not going to dig deep into this fight, both guys have the tools to win in several possible ways and in the end it will come down to who can impose their will. My sense is Okami's looking past this fight and Tanner has nothing else on his mind.
The current odds have Yushin Okami (-200 BetUS) as a fairly significant favorite over Evan Tanner (+190 Bookmaker). The heavy chalk on Okami is due to a mix of current name recognition (yes people forget in just two years), and the fact that this is Tanner's first fight back from oblivion. In reality with both of these guys in shape it's an even match up. For me this is a dog bet I can't leave alone and besides I love to support guys like Tanner.
Prediction: Tanner via TKO.
On the one hand you have to wonder about Tanner's physical fitness, technical acumen and mindstate over this tremendous layoff from top-level competition. On the other hand, Okami's been coasting against guys he matches up well against, by and large. Both Okami and Tanner like the top game, but Tanner is significantly better at inflicting damage on top whereas Okami prefers to control. Tanner had/has(?) better stand-up and is also accustomed to fighter larger men, so Okami's strength won't be a dominating factor like it was when the Japanese middleweight fought Mike Swick. If Tanner is in shape, I absolutely believe he has the skillset to overcome Okami.
I'm going against my own principle here of not banking on the unknown, but you also have to listen to your own instincts. Tanner's got a real shot here. Believe it.