Forever Young

"Forever young/ I wanna be forever young/ Do you really wanna live forever/Forever or never?"
Erin, a girl stuck at 18 years old because of supernatural events that she doesn't understand but saved her life, meets Harry, a British boy, who just like her is stuck at 19 for reasons similar to hers, and the two become friends. Along the way, they start to date and Harry helps Erin to deal with their mutual immorality, which isn't as fun as many would have believed.