He has neck-length black hair pulled back with a weaved design. He has long bangs that go around his face. He has drooping eyes and bags under his eyes. Like all true vampires, René has red eyes, fangs, and pointed ears.
He wears the traditional uniform for vampire soldiers. He has knee-high boots and wears the white cape with the hood down. He has a dark band around either thigh.
In chapter 23, he wears the newer, more form-fitting uniform. He wears a belt with knee-high boots and a hoodless cape that reaches his thighs. He wears his belt so that it is lower on the left. He has a second cape flowing from his waist to his calves.
René holds himself as civil as he speaks in a proper-mannered tone; as well as being calm enough to be capabale of objective judgement as Lacus often leaves decision making to him. Though René sees humans as mere livestock, like all vampires, as well as having a courteous demeanor towards them, he resents humans from the bottom of his heart; which more likely stems from his concern with the fanatical behavior of the humans that he considers dangerous.
He also appears to be obedient when given orders. He does not approve of Mika's behavior in battle, viewing Mika as a greedy former human, who steals the kill and glory for himself. Unlike Lacus though, René is unconcerned about Mika's odd behavior as long as he does his job properly.
His past is currently unknown. However, at some point during his past time, he met Lacus Welt and they became friends. Now, he's rarely seen apart from Lacus.
Story: Vampire Reign
Second Shibuya High Arc
Along with the other city guards, Mikaela Hyakuya and Lacus Welt, René arrives in Sannomiya, Kobe at the to claim that territory for the vampires. Mika slaughters a Horseman attacking a human girl in one swing. The humans cheer that they will now be protected and helped by the vampires just like the humans in Osaka which Lacus laughs at.
Lacus attempts to chat with Mika and fails. René says Mika stole the kill and glory and still has clear greedy human roots, but Mika says he does not care about the glory. Lacus and René shrug, René with a smile, and proceed to inform the new livestock of their rules.
Lacus, René, and Mika follow Seventh Progenitor Ferid Bathory's orders when the attack Shinjuku. Ferid orders Lacus and René to take charge of the human soldiers while he and Mika fight the enemy leader, Lieutenant Colonel Guren Ichinose. 
After they return to Sanguinem from the battlefield, Lacus, René, and Mika all receive curse detoxification. Mika had the worst injuries, and Lacus asks him how he is doing. They do not even know if they succeeded in their mission because they do not know what Ferid's plan was. Lacus continues trying to talk to Mika, who continues to ignore him until being asked what he is. Mika says he is just an ugly bloodsucker, which baffles Lacus. Krul Tepes summons Mika to the Royal Audience Chamber, and Lacus calls him a queen's pet.
They are given an assignment to collect humans from the surface and deliver them to Nagoya. Seeing Mika not drink any blood, Lacus expresses concern while René does not particularly care as long as Mika does his job.
They watch as Mika drinks blood from a vial before dropping it and attacking a human child. He pauses before biting and letting her go, saying he does not need any blood. The choppers take off with the livestock since they met their quota, and Lacus, René, and Mika head to Nagoya on foot. They enter a helicopter at some point off-scene.
Upon their arrival, Aiko Aihara destroys the nearest helicopter, and the three vampires jump down. Mika attacks her while the other two take on the rest of the human cavalry only for the humans commit suicide by swallowing poison.
When the three decide to head to Nagoya City Hall, Aiko Aihara jumps back to life and attempts to hold Mika hostage. René orders him to capture it, and he crushes her wrist, much to Lacus's amusement. She begs for her life and reveals that the JIDA sent an army of fifty to attack the Automobile Museum and assassinate Seventeenth Progenitor Zane Lindau.
They begin to head off, but the human jumps back to life and attempts to kill Mika once again. Mika kills her in retaliation, and they are unable to ask her further questions. Mika claims he cannot trust the word of a human who killed herself and takes five lesser soldiers to investigate Nagoya City Hall while Lacus and René go to the Automobile Museum with the other soldiers.
Three months after the battle at Nagoya airport, Ferid makes a summons to the Progenitor Council. Suddenly from outside, the humans invade Sanguinem. He and Lacus runs in on the meeting, saying the humans are coming to the palace and that he (Ferid) must flee.
- Anime: Four months after the battle at Nagoya airport, he stands atop a platform alongside Ferid, Crowley, Chess, Horn, and René along with a few other vampires. They stand there as a company to greet a fleet of aircrafts that arrives from Europe. From within the aircraft, Lest Karr steps out.
René and Lacus are at Osaka Bay when they see Mika for the first time in three months. The two are in new uniforms with René wearing a white army jacket, and remains silent while Lacus catches Mika up on their plan to retake Sanguinem.
Powers and Abilities
Being a vampire, he is naturally stronger than a human and has the ability to regenerate from non-curse wounds. Although he is not a noble, René is considered to have an extremely high combat ability.
In the anime, René is shown using a sword. His weapons have yet to be revealed in the manga. According to the fanbook, Rene wields a first class weapon.
- René is the French form of the Latin name Renatus which means "born again." It is the male form of Renée.
- Simm is a surname which derives from the name Sim(me), which is a short form of the name Simon.
- To him, Lacus was his first friend.
- Interests/Likes: Blood/Missions
- "What does that matter? He still used to be human. You saw how he stole the kill and the glory for himself. His miserable, greedy human roots show through plain as day."--René to Lacus Welt about Mikaela Hyakuya, Chapter 5, "Vampire Mikaela"
- "Listen, All! This territory will now be ruled and protected by vampires. In exchange for your safety... we request the donation of your blood."--René to the new livestock, Chapter 5, "Vampire Mikaela"
- "Well, that's fine. Mikaela, just do your job."--René to Mika when he refuses blood, Chapter 26, "Thirst Logic"
- "They're only humans, but it is always wise to be cautious on a battlefield."--René to Lacus when they discover the human attack on Nagoya, Chapter 30, "Sword of Justice"
- "Still, they killed themselves. I must admit I find that degree of zealotry mildly disturbing. This 'Japanese Imperial Demon Army' may be trouble."--René to Lacus and Mika after Mika kills Aiko Aihara, Chapter 30, "Sword of Justice"