how do i get the sealed nodachi?

i've seen alot of people with it recently came here to ask where does it drop

i've googled it and so far i still don't know where it drops there's almost no info on it it'd be great if someone can help me

https://pso2na.arks-visiphone.com/wiki/Sealed_Nodachi

Under drop info, most requires UH difficulty lv91+ enemies

The place where I found it to the drop the most was solo Sodam especially at the higher depths