Funding for this research was provided by:
University of the Ryukyus (University of the Ryukyus Research Project toward Post-COVID society Grant)
Ministry of Education, Culture, Sports, Science and Technology, Japan. (the EDU-Port Japan Project as "2021 Research Project")
Received: 23 August 2021
Accepted: 7 September 2021
First Online: 16 September 2021
: Not applicable. The manuscript does not involve human participants or data.
: Not applicable. The manuscript does not contain any individual’s personal data.
: The authors declare that they have no competing interests.