Kaidan Alenko is a fictional character in BioWare's Mass Effect franchise, who acts as a party member (or "squadmate") in the first and third games in the series.

The character is initially introduced in the original Mass Effect as a human Systems Alliance Officer and primary squad member in Commander Shepard's team.

Raised in Canada, Kaidan is a Systems Alliance officer born with the ability to manipulate dark energy, employ telekinesis and create mass effect fields called biotics, after his mother is affected by "Element Zero" during an incident in Singapore while he was in utero.

[1] In gameplay terms, Kaidan is a "Sentinel", who combines biotic and technological abilities to manipulate the environment, enhance defensive capabilities, disable and track enemies.

[3] Kaidan shares the same overall story arc as Ashley in the sequels and while both characters effectively function as opposite-gender placeholders for one another throughout the trilogy, they start off differently in the first game and have distinct personalities and skills.

[7] In March 2017, Jessica Lachenal from The Mary Sue reported that fans have uncovered cut content from the game files of the original trilogy, which reveal entirely voice-acted lines from both Ashley and Kaidan for a same-sex romances relationship with Shepard which never made the final cut of the first game, as well as coded lines where Kaidan would address a male Shepard as if he was female.

After several missions, the squad is ordered to the planet Virmire, where Shepard can assign Kaidan or Ashley to work with the salarians or assemble the bomb that will be used to destroy Saren's facility.

[3] If Kaidan is chosen, he will express survivor's guilt over the fact that Ashley was left behind and killed, having prepared to sacrifice his own life for the rest of the team.

Following this encounter, he will send Shepard a message at the private terminal apologizing for his harsh words during the exchange only if she is still having a romantic relationship with Kaidan.

Following the invasion, Kaidan will accompany Lieutenant James Vega and Commander Shepard on a mission to Mars to find Asari information broker and Prothean scientific expert, Liara T'Soni.

A fully voice acted version of the apology email Kaidan sent to Shepard following their meeting on Horizon in Mass Effect 2 was released by Raphael Sbarge as a sound file on November 24, 2011.

Intended to be a Thanksgiving Day present for Mass Effect fandom, Sbarge said he did not anticipate that the sound file would go viral and that he would receive an overwhelming amount of praise from fans all over the world.

[2] The conditions at BAaT are depicted as poor, and he and his classmates have been treated badly by a turian instructor named Vyrnnus who is openly racist towards his human students.

[2] Kaidan Alenko's characterization throughout the Mass Effect trilogy have received a mixed to positive response from players and video game journalists.

[2] Horowitz went into detail about Kaidan's story arc in the trilogy, and argued that while his subtle characterization and understated nature does not generate as much fan interest as Shepard's other companions, he is "the most developed, well-rounded and fully realized character in the Mass Effect universe".

[9] In an editorial published by This Is My Joystick, Bryony Stewart-Seume drew a comparison to Jane Eyre in order to highlight the actual quality and depth of game writing for the character.

[26][27][28] Kotaku published an article on May 16, 2011, less than a day after developer Casey Hudson's announcement about the game's incorporation of same-sex romances, reporting that some players have spoken out about their concerns that certain characters that have been established over the course of one or both of Mass Effect 3's prequels may undergo "implausible and abrupt sexual transformations" at the expense of "narrative consistency and integrity".

[2][21][30][31][32][33] Horowitz's article for VentureBeat argued that a male Shepard's "friendship, relationship and eventual partnership with Kaidan offers far more depth and reward than the one with Ashley, or arguably any other character in the game by a wide margin".

[2] The Advocate and Gay Community News named Kaidan one of the best queer characters from video games of all time, both praising BioWare's decision to allow players to pursue a same-sex relationship with him in 3 as progressive.

[34] Craig Takeuchi from the Georgia Straight reported on negative reception to the game's same-sex relationship content, which consisted of dismissive and homophobic comments which were posted on several websites.

This is contrasted with Kaidan's more sexualized presentation in Mass Effect 3, where the character is shirtless in multiple scenes, and more emphasis is placed on the intimacy between him and Shepard.