Also add the Vatican, which is somewhat unique
Vatican is without question a monarchy. Its head of state makes no pretense of deriving his (and always will be his) authority from the people. He is elected by a group of men who pray to the Holy Spirit to determine their best choice. And the cardinals are appointed by...previous popes.
Japan's Emperor explicitly has absolutely zero powers according to the post-WW2 constitution. He is purely a symbol of the people's unity and isn't mentioned as head of state. Any reference to government powers being exercised in his name is absolutely taboo.