Is X/1999 hentai?
English title: X: The Movie
No
Rated R+ (Mild Nudity) on MyAnimeList and not tagged as Hentai.

Movie · 1996 · 1 episodes · R+ - Mild Nudity
Action, Drama, Fantasy, Mystery, Shoujo, Super Power
The future of the universe rests on one young man, Kamui Shiro, who must destroy either the Dragons of Earth or the Dragons of Heaven - two opposing armies. He alone must decide whether humanity should be destroyed to create a purified universe, or whether it should be protected to preserve civilization. Two oracles, the sisters Hinoto and Kanoe foresee the coming of the Dragons and predict opposite outcomes. Each sister gathers strength and ammunition to insure her own vision for the future. However, neither sister realizes that there is one man who has an even greater power than the Dragons, and that ultimately he will determine the fate of the earth. Which sister will prevail and how does Kamui fit into their struggle? The answer to this question will forever affect humanity. (Source: Manga Entertainment)
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