OK, Yahoo Japan! There are a lot of cool auctions on YJ! & I will not bid on them for you. Sorry...
I have bid on auctions for some people I *thought* I knew & they flaked. It really pissed me off & I no longer will deal with them.
But there are tons of Deputy Services that will bid for you. I personally recommend Toru @ Anime Dep.
You can also try Celga & Rinkya. I have tried them all in the past & have been generally pleased. If you want your own ID, try Celga's new Gold Account. Very cool idea & if I didn't already have my own ID I would be using them. ^^;; Rinkya has a similiar system (where you can place your own bids) but you do it through their website.
For setting up your own YJ account, please see Drac's Guide to Yahoo Japan. She also runs a Yahoo Japan Deputy Service Forum under Anime Chaos for all things YJ :) Nick (Anime Chaos) also has a Deputy Service, and while I have never used it, I have bought from Nick several times & always been pleased with the service! And Drac is super nice! ^^