Shiretoko is genuinely remote. The nearest significant city is Abashiri on the north coast, about an hour from Utoro by bus. The main rail connection is the JR Senmo Line to Shiretoko-Shari station, from where buses run to Utoro (about an hour). From Sapporo, the journey by train and bus takes around five hours; there are limited direct bus services in summer that cut the time somewhat.
Flying into Memanbetsu Airport near Abashiri is the most efficient approach from Tokyo — the flight takes about 90 minutes, and onward connections to Utoro take about 90 minutes by bus. A rental car from Abashiri or Kushiro gives you the most flexibility for wildlife watching and access to the Shiretoko Pass. Roads within the peninsula are good in summer but the Shiretoko Pass closes from November to late April; once past Utoro toward Kamuiwakka, the road is closed to private vehicles in peak season.