You can only start the vampire route by losing to a specific vampire. Check out the walkthrough for full details.
https://docs.google.com/file/d/1RCKQOJiUVQW5iftBNUX7jkSqGXVr5QGC/edit?usp=docslist_api&filetype=msword
Made 2 saves- one for vampire and one for human route! Never played vampire route before so this will be intersting to say the least!!
Have fun!
