dragon01

Read this:

How to install Daemon Tools

How to mount ISO with Daemon Tools

And lastly, this is very important if you want to play japanese eroge. How to change into japanese locale

If you skip this step, I'm afraid you can't play most of the game in here. Eroge is originally made for japanese people, so it's very normal to change your locale into japanese.

Mount the Sengoku ISO using Daemon and then install it. Next, install the patch. That's all.