• ensure_ascii=Falseを入れると直るかも

import json
 
 
def ecode_json():
 
    with open('a.text', mode='r', encoding='UTF-8') as f:
 
        json_data = json.loads(
            f.read()
        )
 
 
    with open('a.json', mode='w', encoding='UTF-8') as f:
 
        json.dump(
            json_data,
            f,
            ensure_ascii=False,
            indent=2
        )
 
 
if(__name__ == '__main__'):
 
    ecode_json()

import json
 
 
def decode_json():
 
    with open('a.json', mode='r', encoding='UTF-8') as f:
 
        text_data = json.dumps(
            json.load(f),
            ensure_ascii=False
        )
 
 
    with open('a.text', mode='w', encoding='UTF-8') as f:
 
        f.write(
            str(
                text_data
                    .replace(': ', ':')
                    .replace(', ', ',')
            )
        )
 
 
if(__name__ == '__main__'):
 
    decode_json()