Japan’s Overnight Capsule Ferry 😴🛳 24 Hour Travel from Tokyo to Hokkaido 商船三井フェリー さんふらわあ 船旅 大洗→苫&
MOL Ferry Sunflower Sapporo (商船三井フェリーさんふらわあ さっぽろ) is Japan’s overnight ferry that operate from Oarai to Tomakomai, Hokkaido (大洗→苫小牧). It has various class seats from the cheap rooms like capsule hotel to the luxury suite rooms (カプセルホテルルームからスイートルームまで). It takes about 18 hours from Oarai to Tomakomai (大洗から苫小牧).
You can also chose a package tour called the Pacific Story (パシフィックストーリー) that includes the bus transportations from Tokyo Station to Sapporo Station (東京駅から札幌駅). In that case, it takes about 24 hours in total.