This show apparently borrows inspiration from a game, but only for episodes 2 - 5. The first episode is basically filler that doesn't help to set the tone of the story. The episode does not present enough clues for the viewer to solve the mystery on their own, and if you try to watch the anime and are disappointed by its ending, I'd say to drop it right there. The Case Book of Arne doesn't know if it wants to be a shounen or a mystery anime, sometimes mixing both to confusing effects. The episodes inspired in the original source are the best you'll find, buteverything else does not develop the characters and leads to a very unsatisfying conclusion.

Not much to say about the characters themselves, they're all very shallow tropes. The female lead had potential, but since the anime is filler, nothing gets done or addressed in her arc.