Downloaded the linked archive, installed the game off the CD image within...aaaand I'm totally lost as to the file structure going on here. Never heard of a VN engine that used .det files as a main code body, and while OpenOffice Calc will give it the old college try importing them into something CSV-ish, there's no real headway to be had in interpreting the contents when 90% are a mix of non-Unicode control characters and fixed-width ellipses, even when crowbarring them into Japanese character supports assumed to predate Shift-JIS.
Our only shot at salvation is if those are a red herring and all the red meat is in scenario.dat and scene.dat, which have considerably more cogent Japanese sentences interspersed with non-ASCII artifacts.
