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It sounds sort of like Kyou Kara Maou. The main character is a modern-day teen from Japan who travels to a medieval fantasy-esque world, where he discovers he is their king. His magic ability involves jets of water that take the form of Eastern dragons. I'm not sure if there's actually a film; I'm only familiar with the anime series and a bit of the manga.

I remember my family rented some DVD from Redbox (this was probably 2010 or so.). I think the protagonist was a young teenage boy from modern Japan, and there was time travel or something of that ilk, but what I do remember is a scene (the climax or very near to it) where a main character is fighting the big bad who has magic of some sort, and the main character retaliates by using their own magic to make the water in a nearby lake go up in hundreds of rivulets, like gravity got flipped in a polka dot pattern on this lake, and this display of power had something to do with an (Eastern) dragon. The movie ends with the protagonist taking a groupie with a flip phone of himself and a few friends, possibly friends from the past/other world, and the boy returned to his own world/time. One of the people in the pic puts up a V sign next to their face. I think there was an Eastern dragon on the top of the cover, and the title was a Japanese word, not something translated into English words. It's not a lot to go on and vague, but does anyone know what the movie was?
Edited by Lizzie221