No special access issues
Muumilaakso is located in Inkoo, inside the Kopparnäs-Störsvik recreational area. The area has several large parking spaces and there's usually free space at the one closest to the crag. Please don't drive further than that, as there's a locked gate before the shore. The small space at the end of the road is reserved for the people using the boats, and it's an easy walk anyway.
From the marked parking, start walking the gravel road east and after reaching the shore, turn left and follow the small path by the sea to the north until you arrive at the crag. The approach is about 600m, 10 minutes.
Please respect the nature and other people.
More information about the recreational area: https://uuvi.fi/en/area/kopparnas-storsvik/