Japanese names are often more than four characters long, and we have to start with the origin of the name.
The Japanese originally had no names, let alone surnames. Later, in order to manage people, a household registration system was necessary, and people had to give names.
However, most people are illiterate, and it is very troublesome to suddenly have to name themselves and their family members, and they have no way to start. So most people basically just call whatever they see. Those who have fields at home are usually called Soda, those with wells are called Sojing, those who make clothes at home are called Hattori, and those who like animals are called Shiratori, which also expresses beautiful meanings. Yes, the sun, moon and stars can all become surnames.
However, the surname originally takes up two characters or even more, and there are not many characters left for the first name. Everyone wants to give their name a nice and beautiful meaning, but one character is impossible Express all the meanings clearly, so usually two words or more are used. Some people even have a surname with several characters, and when added to the name, it must be more than four characters.