Ace Grit (エース・グリッド, Ēsu Guriddo^?) is a 16-year-old Vestal. He is the Darkus brawler in the Bakugan Battle Brawlers Resistance. His Guardian Bakugan is Percival (later evolved into Knight Percival), and his Trap is Falcon Fly (later evolved into Flash Falcon Fly). Mira Fermin convinced him to join the Resistance one day after defeating him in a brawl, then giving him Percival to prove that Bakugan were sentient and not just mere toys to be played with.

Ace's only major appearance is in Bakugan Battle Brawlers: New Vestroia. Notably, he is also the only member of the Resistance that is not playable in the video game Bakugan: Rise of the Resistance, as he had been captured by the villain Hurranians; the game-exclusive character Eva-Q8 fills in the Darkus brawler position in his place.

Ace is very cocky and hot-headed, which usually gets him into troublesome situations that make him regret the things he says. At first, Ace disliked the idea of having humans join the Resistance, but after tying in a battle with Dan Kuso, he accepts Dan and Marucho Marukura into their group. The similarities between him and Dan have caused tension between them.

He developed a heated rivalry with the Aquos Vexos Mylene Farrow with the two having battled twice and having one win each (Ace only beat Mylene due to Klaus's help). though their rivalry is never truly resolved—Mylene (and her partner, Shadow Prove) would eventually perish after causing Bakugan Interspace to collapse with a dimension bomb following her defeat at Mira and Keith's hands.

He has feelings for Mira, although she is rather oblivious to this fact, and has displayed his protectiveness of her many times through the series. He shown to be jealous of Dan, due to Mira's attraction to Dan, and Keith Fermin, since Mira spends a lot of time with her brother. Because of this, he has a better friendship with Shun, although at first, they did not see eye to eye, mostly because of his cockiness and stubbornness causing him to misinterpret Shun's actions. Ace is sometimes sarcastic, often questions others' ideas, and is also very prideful. He lives alone; this explains his independence and sometimes coldness. But to sum it up, Ace is a good-hearted young person with a proud, stable personality, is not fearful, and is always eager to help his friends.