Detailed information about Hiwatari Kai specifically as he appears in Beyblade the Movie: Fierce Battle cannot be verified from the available sources. The search results contain extensive information about his character from the main anime series but offer very little that is exclusive to the film.

What can be confirmed is that Kai does appear in the movie, though his role is not a major focus. One specific trait attributed to him in this film is a fondness for old legends and prophecies, as noted by another character.

For his character in the broader context of the Beyblade series, Kai Hiwatari is known as the original keeper of the phoenix-like bit-beast Dranzer and is a proud, confident, and highly skilled blader. He is often portrayed as an introverted and mysterious individual who initially keeps his teammates at a distance, largely due to a difficult past and being used by his grandfather for his own purposes. Despite his cold exterior, he has a strong sense of pride and fairness and displays a hidden softer side, such as caring for stray animals. Throughout the series, he undergoes significant development, learning the value of friendship and teamwork, even risking his own safety for his teammates on multiple occasions. His abilities are considerable; he is described as one of the greatest bladers in the sport, capable of making complex deductions and achieving powerful special moves with his bit-beast. However, these character notes are drawn from the television series and cannot be explicitly confirmed as his exact portrayal in the movie Fierce Battle.