Schwarzenegger will be tasked with romancing Thorne's character, a 17-year-old girl with a rare photosensitive skin condition which causes her to have a potentially fatal reaction from exposure to sunlight, meaning she cannot go out during the day. The two begin a nighttime summer romance.
The movie is based off a 2006 Japanese film of the same name.
ET caught up with Thorne to get her reaction to Schwarzenegger's casting and any advice she has for the new star. The 17-year-old actress stayed humble, telling ET, "Patrick is a close friend of mine for a long time. Hardest thing for Patrick will be the hours. He has experience and I would be in no position to give him any advice."
A few weeks ago, Thorne Instagrammed a pic of her and her new co-star sharing a meal
, which she captioned, "With my homie @patrickschwarzenegger if you aren't already following him you should."
The young star was quick to stave off any romance rumors, adding a disclaimer to the photo, "We are just friends :)"