The route in two stages
Tokyo → Shin-Hakodate-Hokuto: Tohoku / Hokkaido Shinkansen Hayabusa.
Shin-Hakodate-Hokuto → Sapporo: limited express Hokuto. Both need seat arrangements.
Allow most of a day. Around 8–9 hours or more is a rough planning allowance including a connection, not a verified departure-specific duration. The Shinkansen segment alone can take about 4 hours; the entire trip is much longer.