Jean Marais plays the Beast but he also plays Avenant who's Belle's (Josette Day) boyfriend and technical antagonist. Technically in this version Belle's sisters are more problematic and Avenant is hardly a Gaston like figure. Avenant's more of kinda of a jerk, but he's not really aggressively evil or anything. Marias's role is pretty limited as Avenant, but still does a pretty job of it. I like that he does not portray Avenant as being overly menacing or anything close to that. Marais instead, rather naturally, showed him to be just a fairly charmless and foolish man. When he invades the Beast's palace at the end of the film Marais's manner is not that of a man who trying to commit some cruel act, but rather that of a fool who is about to make a very serious mistake.
Belle is the one to come in order to save her father, but immediately it becomes obvious that the Beast's demands were less due to a vicious nature but rather those of a lonely man. Marais is terrific in his first scene where Beast meets Bell as instead of that commanding presence he brought in the meeting with her father there is a shyness to his physical manner as though the Beast is ashamed of his appearance while being around a beautiful woman. Marais manages to go from being the threatening monster to a rather somber figure quite efficiently. Marais makes the most of his eyes suggests the strong humanity in the beast as you see the sadness and even fear in the eyes of the Beast as he must face his own image. Marais artfully overcomes the restrictions of his costume and does what he should which is to show the beauty in the beast.
The love story is done in a rather low key fashion, and it is not exactly done as this larger than life romance exactly. Instead it is portrayed as more of Belle coming to understand and sympathize with the beast plight which is made believable by Marais's performance. Marais does a great job of still keeping this certain animal quality with the beast, even as his sweet nature becomes obvious. Marais earns the sweetness he slowly reveals within the Beast which he portrays in a very elegant yet quiet fashion. What works so well is how he brings out the tenderness and meekness really in the beast as he seems to only earnestly urge Belle to love if rather than trying any overt romantic gestures. With the sweetness though Marais is quite moving in his depiction of the Beast slowly weakening resolve and the way it seems that the Beast is far more fearful of the beauty than she is of him.
The chemistry he and Day strike is most unusual really yet so affecting in a rather otherworldly fashion. The connection they create though absolutely works. What I like most in this version though is in the pivotal scene where the Beast becomes the Prince. What I love about is Day and Marais don't quite present it as you might think. Instead of instantly embracing each other or anything like that there is instead a certain awkwardness both actors bring to the scene. This awkwardness is a good thing though kinda making it like the beast now as the Prince does need to reintroduce himself again since he has become a man again. Marais brings a certain hesitation as if the Beast is making sure she still loves him even though he's no longer the beast. Both of their performances in this scene allows them to earn their happy ending much more as they take the moment to recognize the transition, and give it the wondrous quality it needs.