Joseph is the third coach the franchise has had in as many years, after he succeeded Mark Hammett and Filo Tiatia.
Current Sunwolves assistant Tony Brown shapes as a likely replacement moving forward.
Joseph told a press conference in Tokyo: “I won’t be coaching the Sunwolves next year, but I will be involved in appointing the coaches.”
The conference marks one year until Japan open their 2019 Rugby World Cup campaign on home soil.
The 48-year-old New Zealander said: “Some of my staff will be involved with the Sunwolves.
“What has always been challenging has been giving our national players the opportunity to play Super Rugby without giving them too much rugby,” he said.
“Next year we need to be peaking about now, in September, and certainly not in February when the Super Rugby competition starts, so you can expect a number of our players will not be participating at the start of the Super Rugby competition with the Sunwolves. But they will start a bit later in the season.”
Joseph led the Sunwolves to three victories in 2018 – their most successful yet as they beat the Reds, Stormers and Bulls. Despite the improvement, they still finished last on the table.
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