As a Danish national it is possible to enter Japan for a period of 3 months (90 days) or less without first obtaining a visa for the following purposes:
Sightseeing, recreation, amateur sports, visiting relatives, short-term study, inspection tour, participation in unpaid lectures or meetings, attending a conference, business contact or other similar activities.
Upon arrival at immigration in Japan, such a passport would be stamped for a stay of ninety days.
On entry to Japan a traveller should possess a fixed-date, confirmed return or onward journey ticket, and any supporting documents, which can serve as evidence of the purpose of the trip (such as conference details, details of the host organisation etc.) Furthermore, a traveller may be asked to show evidence of sufficient funds for the proposed period of stay in the country.
A visa is required if your purpose of travel is as a long term resident, for long term study, for volunteer activities, for employment or other remunerative activities.