A War In A Basement

Astrid, a normal teenage girl moves in with her father, due to her mother's death. Astrid knew that her parents were divorced, and she knew the pain, because she broke up with her boyfriend the same day as her mom died. Astrid never knew her father until now. When she takes a walk around the house, she accidentally locks herself in the basement, where she can't even call her father.
That's when the fiasco begins. An old man pops out of nowhere and drags Astrid into some kind of portal that teleports them both to a world that changes Asrid's life. This is where she meets Astley, who turns out to be a better boyfriend anyone could have. Astrid forgets her sorrows shortly after the two start communicating.
But the problem is the war where Astrid might lose Astley forever.