In anime XYZ, W person behaved this way.
Why did he do so, is this common in Japan?
Is this kind of question on-topic?
Yes, questions in regards to the Japanese culture are considered on topic.
As the tag excerpt reads:
Questions about anime and manga in the broader context of Japanese culture. Includes both questions about cultural origins for anime/manga references and questions about the cultural impact of a particular series.
In certain cases, it might also relate to the tropes as this is all about re-occurring events
Tropes: A recurring element across anime, manga or works in other media. Tropes cover clichés, genre conventions and other recurring plot points, character types, narration styles, …
If you have a such a question, you can take some inspiration from questions Tagged as culture+tropes.