Required is not recommended: the first is what the border asks about, the second is what a clinic would suggest. Both, for Japan, then the number to dial and what care costs a visitor. Applies to every guide in Japan: Tokyo, Kyoto, Osaka, Hiroshima, Nara, Hakone and 5 more.
Required to enter
Nothing. No vaccination certificate is asked for at the border.
Recommended
Routine vaccinations up to date
Japanese encephalitis only for long rural stays in summer
Emergency number
119 for fire and ambulance, 110 for police
Care for visitors
Good and affordable
Superb, and ambulances are free. Treatment is not: visitors pay in full up front, and hospitals routinely refuse cards, so carry cash and real insurance. Finding English-speaking staff outside major cities is the harder problem — the JNTO medical directory is worth bookmarking before you go.
The general rules — clinic timing, water, mosquitoes, insurance — are in travel health tips.