Here are the top ３ ways to say WHY in Japanese
Japanese people deeply respect harmony in their society. That is why, asking people WHY perhaps is not as common as other societies. People come to wonder how the Japanese say why. Here it goes
1: Naze: なぜ: Why
2: Nande: なんで: Why
3: Doushite: どうして: Why
Also if you are in Kansai Region (the Southern Part of Japan where Kyoto, Osaka and Kobe are located) and speaking Kansai Dialect (Kansai-Ben) you’d say
NANDE YANE!!! なんでやね！This is saying “why” in a very surprised but kinda non-threatening way.