Game was stealth patched on DLSite apparently game is able to be cleared legit now:
・08/15 update version
The events for Kokin Doppo Tadakatsu and Dokuganryu Masamune have progressed and can now be captured.
The escape event for Saburo Nobunaga will no longer occur, and you will no longer be able to fight the Rokutenmaou Nobunaga Defense version.
As a result, if you capture Saburo Nobunaga, Gracia, Mitsuhide, and Takeda Shingen will no longer appear.
If you capture Ranmaru and Yasuke without capturing Saburo Nobunaga and clear the first battle at Furuwatari Castle,
Azuchi Castle will appear, and the three will appear afterwards.
Google Translate butchered names but you get the idea.