Is Saber Marionette R hentai?
No
Rated R+ (Mild Nudity) on MyAnimeList and not tagged as Hentai.

OVA · 1995 · 3 episodes · R+ - Mild Nudity
Comedy, Harem, Mecha, Sci-Fi
Jr., the heir of Romana and his battle sabers Cherry and Lime, who have girl circuits are enjoying their peaceful life in Romana. Suddenly, the evil Star-Face and his sexadolls attack Romana in order to take over so Star-Face can become the next High Official. In order to truly become the next High Official and ruler of Romana, he must first eliminate Jr. This begins a battle for, not only Jr.'s life, but for all of Romana. (Source: ANN)
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