It was a fun watch, while this movie is a pretty good retelling of the beginning of the story I do think you'd have to watch season 1 first if you want to properly understand the lore. The whole "humans making contracts with supernatural beings and defeating them" trope does honestly feel a bit too generic, specially for 2007, however I think it manages to make itself different enough from the bunch of anime following similar plots. The artstyle is peak mid 00's Moe despite the plot having heavy dark fantasy and tsundere heroine action. I personally remember every anime from the time looking like this so I'm nostalgic for the entire experience as it manages to pretty much take every popular light novel trope from the time and adapt it in a way that feels fun and lively instead of generic. I specially appreciate how they manage to fit darker themes while not making it overly serious and still engaging in lighter romance and comedy gags. You can definitely skip this movie if you've already watched the first season, but I do think it offers a worth watching experience if you enjoyed the series or the light novel.