Resident Evil 4 revisits a few old friends, and also introduces some brand new ones. The characters in Resident Evil 4 are certainly alive with intent and emotion, so getting to know them is of importance. Each character seems to have his/her own story, but more will be revealed as you progress through the game.
Leon Scott Kennedy
Leon is one of the two leading characters featured in Resident Evil 2; the other being Claire Redfield. In the story, Leon is a recently-hired police officer for the Raccoon Police Department. He arrives late to Raccoon City on his first day of duty, already dressed in the armored R.P.D. uniform issued to him. He finds the town already overrun by zombies and encounters another living civilian, Claire. The two decide to seek refuge in the city's police station, as they attempt to escape the city alive. He maintains radio contact with Claire and is partnered with Ada Wong, a woman claiming to be looking for her missing fiancee. His attempt to find an escape route leads to Umbrella's underground laboratory within the city, where he confronts several of Umbrella's mutant creatures, including a mutated William Birkin. Just prior to making his escape, Leon learns that Ada is actually a corporate spy sent to steal the G-Virus. However, Ada is fatally wounded and presumed dead, leaving Leon to escape the lab by himself along with Claire and Sherry.
The epilogues of Resident Evil 3: Nemesis expand on Leon's fate following Resident Evil 2. After escaping the city, Claire set out on her own to search for her brother, while Leon and Sherry were approached by the U.S. Military, and Leon made an undisclosed deal with a representative of the U.S. Government. In Resident Evil: Survivor and Resident Evil Code: Veronica we learn that Leon has joined an "Anti-Umbrella" force. In Survivor, he is mentioned to be the one who sent the game's protagonist, Ark Thompson, to go undercover into Sheena Island (the game's setting). Likewise, in Code: Veronica, Claire gets in touch with Leon when she is trapped on Rockfort Island, and in turn, Leon relays her information to Chris.
Leon's next game appearance depicts him as an "Anti-Umbrella" agent in the non-canon Resident Evil Gaiden, an alternate universe gaiden installment released for the Game Boy Color. In Gaiden, Leon goes missing during a mission aboard the Umbrella cruiser Starlight. Barry meets up with Leon and the two team up to take down a new type of Bio-Organic Weapon infesting the ship, and escape along with an orphaned girl named Lucia. The game's ending shows a close-up of Leon's neck bleeding green blood, indicating that he was infected by a virus before Barry came to rescue him.
Leon would return to the official canon as the protagonist of Resident Evil 4. The game revamps not only the established Resident Evil gameplay formula, but also the series' ongoing storyline. Set six years after the events of Resident Evil 2, Leon has since become an agent for the U.S. Government and is assigned to rescue the newly-elected President's daughter, Ashley Graham, who is being held in an undisclosed village in Europe. Her kidnappers turn out to be part of a religious cult known as the "Los Illuminados", which has taken control of the local villagers with a breed of parasites known as Las Plagas. Leon teams up once again with Ada Wong, who seeks to steal a sample of the parasites for her unknown employer, as well as with a Spaniard named Luis Sera, a former researcher for the cult. He also confronts Jack Krauser, a former acquaintance who disappeared two years prior to the events of the game and is now in league with the cult. Leon fulfills his mission by eliminating the cult leader, Osmund Saddler, and escaping the cult's island headquarters with Ashley Graham.
Ashley Graham (voiced by Carolyn Lawrence) is the 20-year-old daughter of the newly-elected President, taken captive by the Los Illuminados during her trip home from Massachusetts and held in a European village. It is Leon's initial objective in the game to ascertain her whereabouts and retrieve her. After meeting her, it is revealed that she has been implanted with a Plaga parasite, so that the cult could gain control of her before returning her to the U.S.. The rest of the game then becomes a quest for Leon and Ashley to find a way to remove the parasites inside their bodies before they fall under Saddler's control. When Ashley is with Leon, it is the player's duty to protect her. As with previous Resident Evil games that feature short sections in which the player takes control of a supporting character, the player takes control of Ashley in a chapter of the game.
Luis Sera (voiced by Rino Romano) is a 28-year-old Spaniard who befriends Leon early in the game and teams up with him to escape the village. He betrays Saddler and steals the sample of Las Plagas, but eventually Saddler catches up, and kills him. While dying, Luis gives Leon medication to suppress the growth of the Las Plagas.
The "Separate Ways" scenario and "Ada's Report" documentary added to the PS2, PC and Wii version of the game expands on Luis's role in the game, depicting him as in league with Ada Wong and the organization she works with (a connection that was only implied in the main game).
Ingrid Hunnigan (voiced by Salli Saffioti) is Leon's primary radio contact and his only link to headquarters. She provides the player with general gameplay tips and hints between chapters early in the game. Leon loses contact with her after he first enters Ramon Salazar's castle in which the communication line is hijacked by Los Illuminados. Salazar (and later Saddler) takes over the transmission to taunt Leon between missions. Leon does not regain contact with Hunnigan until after the end credits.
Ada was first mentioned by name in a document entitled "Researcher's Letter", in the original Resident Evil. The letter, written by a dying researcher named John, is addressed to his girlfriend and co-worker Ada.
Ada would make her first appearance in Resident Evil 2, serving as the partner character in Leon S. Kennedy's scenario and as a playable character during certain sections. Under the guise of an ordinary citizen, she requests Leon's aid, claiming to be looking for her missing fiancée in Raccoon City. However, she learns that John died during the Mansion Incident (Resident Evil) and attempts to escape the city with Leon. She develops romantic feelings for Leon, but gets injured during a battle against the mutated William Birkin. Later it is revealed that Ada is actually a spy for an unnamed organization, sent to retrieve the G-Virus sample. She does not escape with Leon and the others and is presumed dead at the outcome of the game. Her on-screen death differs depending on the order in which Leon's half of the game is played. In the Leon A scenario, she confronts Leon before being shot by Annette Birkin and falls to her death from a catwalk. In the Leon B scenario, she confronts the Tyrant, before being mortally wounded and dying. Despite her apparent death, she comes out of the shadows to help the player's character near the end of the second scenario by providing the rocket launcher needed to destroy the Super Tyrant. Ada is also a fully playable character in the "Extreme Battle" minigame added to later versions of the game.
A character-specific epilogue in Resident Evil 3: Nemesis does confirm her survival and Wesker's Report, a fictional documentary published to promote the release of Resident Evil Code: Veronica expands on Ada's role in Resident Evil 2. The organization Ada works for is revealed to be the same one that hired Albert Wesker in Code: Veronica. Moreover, Wesker worked with Ada behind the scenes to retrieve the G-Virus and it was he who saved her life.
Ada returned alongside Leon in Resident Evil 4. Taking place six years after the events of Resident Evil 2, the game reunites the two characters, as Ada assists Leon on his mission to rescue Ashley Graham. However her true objective is to retrieve a sample of the Las Plagas parasite from cult leader Osmund Saddler and she does fulfill this mission in the end. While not playable in the main game, Ada has the starring role in the minigame "Assignment Ada", which depicts Ada retrieving the sample for Wesker. Another minigame, "The Mercenaries", features Ada as one of five playable characters. When Capcom ported the game to the PlayStation 2 and the Wii, a third minigame titled "Separate Ways" was added. This depicts Ada's actions during the main storyline, featuring new plot revelations. "Separate Ways" is supplemented by the five-part "Ada's Report", in which Ada reveals several secrets, including how she does not supply Wesker with the virus sample that she retrieves in the game, and that she is actually working for another organization against Wesker.
Bitores Mendez (voiced by Jesse Corti) is the village chief whom Leon faces at the beginning of the game. Some of his distinguishing characteristics include his imposing stature, fake left eye and resistance to firearms. He leads the hunt for Leon and Ashley early in the game, leaving behind notes of his strategies to trap the two.
Ramon Salazar(voiced by Rene Mujica) is the eighth castellan of the castle which serves as the setting for part of the game. Ramon's ancestor, the first castellan, was responsible for sealing the Las Plagas parasites in his castle centuries ago. Despite his diminutive stature and wrinkled face, he claims to be only 20 years old. He is protected by two cloaked bodyguards known as Verdugos.
Jack Krauser (voiced by Jim Ward) is a mercenary hired by Saddler and is the one responsible for Ashley's kidnapping. A former U.S. agent, he was once a close friend of Leon until he was presumed dead two years before the events of the game and disappeared. In reality, he infiltrated the cult in order to procure the sample of "Las Plagas" and is actually working for Albert Wesker. In addition to being a skilled knife fighter and archer, Krauser is also endowed with the ability to transform his left arm into a giant mutated sword-like claw. Leon fights him twice during the course of the game: first in an interactive cut-scene which depicts a knife fight between the two, and later in an in-game battle across a set of ruins on the island. At the end of this battle, Krauser is assumed dead. However, in the 'Separate Ways' mini-game he battles Ada in his defeated form, suggesting that this battle takes place after he battles Leon for the second time.
Krauser appears as the end boss in the "Assignment: Ada" mini-game. He is also a playable character in the "The Mercenaries" mini-game, in which his claw can be used as a special attack by the player. In addition, the "Ada's Report" documentary expands on Krauser's role in the storyline.
Osmund Saddler (voiced by Michael Gough) serves as the main antagonist of Resident Evil 4. He is the leader of a religious cult known as Los Illuminados, which seeks to control the world. He has converted the villagers into his cult and now controls them through the Plaga parasites in their bodies, using special radio frequencies from his staff.
A mysterious character who's identity or true intentions are unknown. The Merchant will be encountered frequently throughout the game. The player will be able to buy, sell, and upgrade weapons from him. The Merchant can be killed and will not spawn at the location again (but can in future locations). If the Merchant is killed in Professional Mode, he will never spawn again in any location.
Two officers from the Spanish police are assigned to bring Leon to the village where Ashley had been seen. They don't take the assignment very seriously though and when they arrive they prefer to stay in the car while Leon goes to the village. This turns out to be a very unfortunate decision for them.