I guess they are expanding, they setup another Sonia II beside Sonia. The staff has also shifted over to Sonia II. So even if you have booked Sonia, you will need to go Sonia II to check in. (there is a board in front asking guest to proceed to Sonia II)
Super spacious areas
Well equipped toilet accessories
View from the hotel
It is 10mins walking distance from the Otaru JR station.