Thank you so much for responding to request and sharing!!! Love you!
DLC works perfectly, tested with save from seiya-saiga. For anyone wondering, how to access it, you have to click on the heroine's sprites on the main menu screen after completing main game and then you can watch her DLC scene. I think there is one for every heroine.
Also for those having trouble with PlayDRM, you can do one of two things, either copy all the CV files and patchdlc01.fpk file from the DLC folder to your main game folder, but you can bypass the PlayDRM very easily too. For that, just download any of the game's update patches which is free to download from Candysoft official patches download page (
https://www.candysoft.jp/ohp/05_Download/05patch.html) in there, look for kamishippo102.zip, now in that folder, there is one Update.exe file which is 91kb in size and does NOT have PlayDRM, so just replace the Update.exe file in the DLC folder (which is 2 mb in size and has PlayDRM) with the patch folder one, and then you can run it and install from there properly without needing to manually copy over the files. It takes some time though for DLC files to get installed since it is quite large, so please be patient and don't worry since you can see the Update.exe running in task manager. After that you can install the other update patch as normal. Hope that helps someone and enjoy playing the game!