Just a few directions you could look.

The Classic and Pre-Classic Maya generally viewed their kings as intermediaries to the gods. Not exactly the same, but there is some evidence for the deification of dead rulers. For instance, the famous sarcophagus lid of the king of Palenque, Pakal, which shows him being reborn as the maize god.

The Inca emperors are descendants/representatives of the sun god Inti.

Sumerian kingship was largely based on the divine or semi-divine status of Sumerian kings.

The "Mandate of Heaven" concept in China isn't exactly what you are looking for, but similar. For the Japanese emperors it is taken literally, as you already suggested, but it could be interesting to compare the literal interpretation with the less literal take of the "Son of Heaven" idea in China.

Along similar lines, the European concept of "Divine Right" (e.g. Louis XIV) isn't exactly what you are looking for, but it could be interesting to compare with these other examples. Perhaps you could also discuss the role of the Pope as representative of God on earth.

There are probably quite a few more, but these are at least a few direction to start. I don't have enough knowledge to give you a lot of literature on these topics, just enough to point them out as possible areas of research, but go ahead and ask and hopefully someone more specialized can give you some information.

Edit: Also take a look at the Khmer and their idea of their kings as incarnations of Vishnu or Shiva.

Sorry, we don't allow throughout history questions. These tend to produce threads which are collections of trivia, not the in-depth discussions about a particular topic we're looking for. If you have a specific question about a historical event or period or person, please feel free to re-compose your question and submit it again. Alternatively, questions of this type can be directed to more appropriate subreddits, such as /r/AskAnthropology, /r/history or /r/askhistory.