Maezawa here.
Please allow up to one week from the interview to registration.
(Usually, registration can be completed the next day, but it may take longer due to various circumstances.)
If you mean the beginning of January, then it’s already been a week.
Some branches have recently changed their LINE accounts, so if you registered through the old LINE account, they may not have been able to contact you.
Unfortunately, it’s also possible that your application was not accepted.
First, try asking what’s going on through the LINE account you used to register. If you don’t receive a reply after waiting a day, the Universe Club LINE account may have changed, so could you try calling them?
For Tokyo, you can reach them at 0120-966-531. If it was another branch, you could look up its phone number on the website, or call the Tokyo office and ask for the number of the branch where you had your interview.