In 2014 and 2015, Reckoning appeared in the WWE a number of times as one of Adam Rose's rose buds. She also worked as enhancement talent for WWE's developmental territory NXT at the October 2014 television tapings, losing to Charlotte.
On July 13, 2017, she returned to WWE by entering the Mae Young Classic tournament as Mia Yim, defeating Sarah Logan in her first round match. The following day, Yim was eliminated from the tournament in the second round by Shayna Baszler. On August 9, 2018, Mia Yim once again returned to the WWE by entering the Mae Young Classic tournament for the second time, defeating Allysin Kay in the first round and the returning Kaitlyn in the second before losing to Toni Storm in the quarterfinals.
Thanks to her performance at the Mae Young Classic, on September 24, it was confirmed that Yim was signed to a contract with WWE and would begin working on NXT. Just a month later, on the October 24 episode of NXT, Yim made her in–debut as part of the brand, defeating Aliyah. In November, after a backstage altercation between the two, Yim faced Bianca Belair who would hand her first loss and that would also spark a feud between the two. Yim was able to bounce off the loss and defeat Reina Gonzalez to earn herself a spot for an upcoming fatal-four way match to determine the number one contender for the NXT Women's Championship, however, the match was won by Belair. Shortly after Belair's undefeated streak was ended, Yim was able to defeat her in two different matches to end their feud.
On August 10, 2018 at NXT TakeOver: Toronto, Yim lost to Shayna Baszler in an NXT Women's Championship match. In November, Yim made her main roster debut as part of the NXT talent that were placed in an invasion angle with Raw and SmackDown as part of the Survivor Series pay-per-view. Yim was chosen by Rhea Ripley to join her team for the first-ever women's WarGames match against Shayna Baszler's team. On November 23 at NXT TakeOver: WarGames, just before the match took place, Yim was attacked backstage and unable to compete in the women's WarGames match. However, Yim was replaced by Dakota Kai on Team Ripley, who eventually turned on Team Ripley and attacked Tegan Nox. Eleven days later on the December 4 episode of NXT, Yim revealed that Kai attacked her backstage and this led to a grudge match between the two, which Yim lost. On June 7 at NXT TakeOver: In Your House, Yim teamed up with Tegan Nox and Shotzi Blackheart and defeated Dakota Kai, Raquel Gonzalez and Candice LeRae in a six-woman tag team match.
On the September 21, 2020 edition of Raw, several weeks after her last appearance on NXT, Mia Yim turned heel in her main roster debut by revealing herself as a member of the villainous stable Retribution, under the ring name Reckoning. She made her ring-debut on the November 30, 2020 episode of Raw, in a losing effort against Dana Brooke. Throughout February and March, tension was teased among the group as the group's leader, Mustafa Ali, would publicly berate the rest of the group whenever they lost a match. This culminated at Fastlane, when Reckoning walked out on Ali along with Slapjack, while Mace and T-Bar gave Ali a double chokeslam, effectively disbanding the group.
On the October 4 episode of Raw, Reckoning was officially drafted to the Raw brand as part of the 2021 WWE Draft, reverting back to her old ring name Mia Yim. On November 4, Yim was released from her WWE contract without ever reappearing on television.
On the November 7, 2022 episode of Raw, Yim returned to WWE as a face, attacking Rhea Ripley of The Judgment Day and aligning with The O.C. (AJ Styles, Luke Gallows, and Karl Anderson). Three weeks later at Survivor Series WarGames on November 26, Yim's team defeated Ripley's team in a WarGames match. On January 28, 2023, Yim entered the women's Royal Rumble match, entering at number twenty-three and lasting for more than seventeen minutes before being eliminated by Piper Niven. In the following weeks, her ring name was tweaked to "Michin" Mia Yim. As part of the 2023 WWE Draft, Michin was drafted to the SmackDown brand. On the December 22 episode of SmackDown, Michin pinned WWE Women's Champion Iyo Sky in an eight-women tag team street fight against Damage Control, granting her a title shot at SmackDown New Year's Revolution on January 5, 2024, where she failed to defeat Sky for the title.
On the May 28 episode of NXT, Michin defeated Tatum Paxley to qualify for a spot in the six-woman ladder match to crown the inaugural NXT Women’s North American Championship at NXT Battleground but failed to win the title at the event.