How to apply a koseki tohon

Hi,my second Japanese husband adopted my child who is a Japanese passport, and we just got divorced, my child who is already 24yr old and wanted to have her own Koseki tohon and use her real last name from her biological father, how can she apply for this, thank you!

adoption and nationality are independent.
if your child has a Japanese passport, it means she was naturalized to Japan.
Is that true ?

I mean her biological father is a Japanese also, and she was registered as Japanese citizen before she was adopted by my second Japanese husband,now that I got divorced she wanted to use her last name from her biological father again,how can it be possible,and how is the procedure?

ask city hall I would say

養子縁組の解消
ask the city office where you took the divorce paperwork.
since your child is an adult, she can ask them by herself.
having a koseki tohon is also easy. she can do it by herself.

Thank you very much to all for sparing time to this question ,have a warmly night