Ciel

Doctor Ciel (シエル Shieru) is a fictional character in the Mega Man Zero video game series. Although not a playable character, she is considered the female lead and heroine of the series, having important roles in most of her appearances, being the deuteragonist of Mega Man Zero and a non appearing but still major character in Mega Man ZX.

Origin
According to the "Mega Man Zero Official Complete Works" source book, Ciel is a product of Neo Arcadia's technological advancements, which is what allowed her to attain such a high level of knowledge at such a young age. With the goal of creating an utopia for humans and Reploids, Neo Arcadian researchers began to produce humans with altered DNA. Some of these humans were children born specifically to develop better Reploids to assist in the research. Ciel was one of these children, and stood out as a prodigy, being able to learn just by watching and mimicking experiments. Ciel became a Reploid researcher that worked for Neo Arcadia. When Mega Man X disappeared some years before the events of Mega Man Zero begins, Ciel created Copy X to replace him when she was nine years old. Additionally, one of her ancestors, another female scientist, was apparently directly responsible for the creation of the original Mother Elf, from which all other Cyber-elves were spawned.

However, when Copy X began oppressing and executing Reploids to solve Neo Arcadia's energy crisis, Ciel felt very guilty that her own creation was behind it, so she migrated with Reploid refugees to a ruined city. Knowing they were being falsely accused, Ciel decided she could not stand by helplessly, so she formed the Resistance, acting to free Reploids from Copy X's regime. She soon became something of a mother figure to many of the Reploid refugees in the organization, especially a young girl she named Alouette. Times grew more desperate, though, and she eventually found her only hope to be uncovering a legendary hero that most people didn't even believe in anymore: Maverick Hunter Zero. She sought and eventually found him, though it took the sacrifice of one of her Cyber-elves, Passy, to wake him up.

Doctor Jesus: Rebooted
It is known that she is a retired Team Rivper's member since she retired because she does not like the team, due to animal abuse and she wanted to retire and move to Team Villalba. In the past, she was a Team Rivper's member before she retired

She moved to Team Villalba since Ingrid Giraffe broke Police Jesus's heart because she cheated on him with Adam Lyon, and in the end Police Jesus' relationship with Ingrid never came back because of Adam (nor could he get her back because he was too invincible). Ciel finally fell in love with Police Jesus and fixed his heart! Therefore, she supports the rival team in the fight against animal abuse, becoming an antagonist along with Police Jesus and the rival team's members.

Trivia

 * Ciel was only nine years old when she created Copy X, and she was able to create him by watching and mimicking experiments. The idea and explanation for this notable feat had to be figured out quickly by Inti Creates when they decided to change the final boss of Mega Man Zero from the real X to a copy. Then she was decided to be a genetically modified child from Neo Arcadia.
 * She is 14 in the first game, 15 in the second and third, and 16 in the fourth. Her age during the Mega Man ZX flashbacks is unknown. (According to the Developer Interview in the Remastered Tracks Rockman Zero TELOS CD Booklet).
 * Ciel was originally intended to be a cyborg.
 * Ciel is one of the few human main characters in the main Mega Man timeline; like most of them, she is also a scientist.
 * Ciel holds a few notable similarities to Dr. Thomas Light of the classic Mega Man series. Aside from both being pacifistic scientists of their time, they provide aid for the heroes generations in the future (Light provided the armor upgrades to X and Zero; Ciel created the 6 Biometals).
 * Ciel bears a slight resemblance to the numerous incarnations of Roll as well as Alia. In fact, before gaining a name, she was nicknamed "Roll" during the first game's development.
 * Early in the first game's development, Ciel was considered to be a playable character as a Cyber-elf user that, as an opposite of the swordsman-like Zero, would act like a wizard, with Cyber-elves being the magic abilities. An enemy Cyber-elf user was also considered.
 * In Ciel's room in the old Resistance Base, a Resistance uniform (decked in the organisation's green color) is visible hanging next to her bed. Presumably, this belongs to Ciel herself, but the reasons why she prefers her traditional outfit over this one is unknown.
 * Labo, Ciel's theme from Mega Man Zero 2, was based on Rebecca's theme from Resident Evil.
 * Throughout the series, Ciel is shown to have romantic feelings for Zero, regardless of the fact that he's a Reploid and she's a human (such as in the ending she says "I" then hesitates before continuing "I believe in you" possibly signifying she was going to say "I love you").
 * Translations for the lyrics of Zero 4's ending theme sang by Ciel's voice actress Rie Tanaka, "Freesia", blatantly spell out these feelings.
 * During Mega Man ZX Advent, there's a stained glass window in the background of the 8 bosses rematch in Ouroboros. Featured in that artwork is a woman strongly resembling Ciel.
 * Ciel shares many similarities with Lacus Clyne from Mobile Suit Gundam SEED and SEED Destiny. They have the same voice actress Rie Tanaka, have feelings for the main protagonists, both were genetically modified, and lead their own organization.
 * Joule, a character from Azure Striker Gunvolt is likely based off Ciel. Both are the main heroines of their respective games who develop feelings to the protagonists (Ciel to Zero and Joule to Gunvolt) with an extraordinary abilities. Both of their voice actors (Rie Tanaka for Ciel and Megu Sakuragawa for Joule) are also well-known singers.