Note: It is Departing From Tokyo to Sydney. So you will have to combine with another one way ticket to go from Sydney to Tokyo.
Malaysia airline Business Class
After late May on most dates. It is available not only from travel agencies but also on their official website.Oneway is from $1637
Return is from $2429 (It seems you can 'stay' in Sydney for maximum of 3 months. could be best value when travelling Syd->NRT in peak season. )Cathay Pacific Business Class
Return from $2614 (Oneway is not found at bargain price. Also, this price is only available from travel agencies.)
Good for Oneworld status run?