Mars was first introduced during Black Clover's Dungeon Exploration arc as the herald of the next big villain in the series, the Diamond Kingdom, but the latest arc of the series has seen a dramatic shift for the character.
Completely flipping against the Diamond Kingdom, the latest episode saw Mars and Asta surprisingly work together in order to save Fana of the Eye of the Midnight Sun from blowing herself up.
In the latest episode of the series, it's revealed that Fana was actually Mars' friend back in the Diamond Kingdom. She was one of his fellow students that he had to kill in order to graduate out of the harsh training program, and seeing her again awoke something in Mars. Fueled by this desire to save her, he and Asta worked together to approach her.
As Fana prepared to self-detonate after first being defeated by Asta (much like Vetto did during the Seabed Temple arc), Mars and Asta slowly approached her to get her to stop. The heat of her flames was strong, and it burned the two as they approached, but Mars cloaked he and Asta in his Phoenix Robe magic in order to heal them as they were being damaged.
In this moment, which was also the first time they have seen one another since the Dungeon Exploration arc toward the beginning of the series, the two came to a mutual respect of one another. Mars notes how brave Asta is in the face of adversity, and his desire to never give up made was one of the few Magic Knights who actually deserved the title of "Knight."
Asta, looking over to Mars, notes that he's no longer the cold, killing "doll" that he was during their first meeting. He says Mars is stronger than ever because of his desire to save Fana, and thankfully the two do just that. Mars is eventually able to talk Fana down from exploding, and Asta cuts through her magic with his anti-magic sword.
In this moment, Mars takes the opportunity to hug her and this brings all of Fana's memories of Mars back to her. This snaps her out of whatever weird mind control spell she was under, and thus the first (and hopefully not the last) team up of Mars and Asta ended with a decisive victory.
Yuki Tabata first created Black Clover for Shueisha's Weekly Shonen Jump magazine in 2015. The popular series follows two young boys named Asta and Yuno who are growing up in a world where magic is everything. Asta, unfortunately, seems to have been born without magical powers while Yuno is a young prodigy whose magical powers rival that of the strongest magic users in the Clover Kingdom, the Magic Knights. The two young boys now strive to become the strongest wizard in the Clover Kingdom, The Wizard King.
You can currently find the Japanese language version with English subtitles on Crunchyroll, and the English language dub can be seen on FunimationNow and Saturday evenings on Adult Swim's Toonami block.