Which or storefront (Steam, Nutaku, etc.) are you running?
Character data in AI*Shoujo is tied to PNG images embedded with hidden data. If you downloaded a character save, make sure the .png file is placed in UserData/chara/female/ or UserData/chara/male/ . Do not rename these files drastically, as it can sometimes break the metadata link. ai shoujo save file
The save data is not stored in the game's root directory but in the Windows user application data folder. Which or storefront (Steam, Nutaku, etc