Japan referred to its own ruler as “the Son of Heaven from the land where the sun rises” and described the Chinese emperor as “the Son of Heaven from the land where the sun sets.” This phrasing was a diplomatic way of positioning themselves as equals.
こんにちは！
ご質問ありがとうございます。
ご質問について、いくつか言い方が考えられますが、例えば、
In ancient times, Japan saw China as a powerful presence in the region. To assert equal status, Japan referred to its own ruler as “the Son of Heaven from the land where the sun rises” and described the Chinese emperor as “the Son of Heaven from the land where the sun sets.” This phrasing was a diplomatic way of positioning themselves as equals.
とすると、「[古代](https://eikaiwa.dmm.com/uknow/questions/86909/)日本では中国を脅威と考えていたため、それぞれ「日出ずる処の天子」「日没する処の天子」と表現して対等であろうとした」となります。
参考になれば幸いです。
日本 
