A kid and an alien symbiote become one weapon, and the show treats it like the most fun thing that could ever happen. Hiroyuki Sawano's soundtrack doesn't just underscore the action, it becomes the reason you remember the fight, turning every collision into something that lands in your chest. The animation moves with such confidence, every frame of movement costs something, and you feel the weight of every punch before the impact hits. This is shonen stripped to what it does best: two unlikely partners learning to trust each other while everything explodes around them.

Long ago, alien organisms came to Earth and merged with people, and because the fused beings resembled mechanical limbs, they became known as Mecha-ude. Ordinary middle schooler Hikaru Amatsuga ends up in an unwanted partnership with Arma, an exceptionally rare Mecha-ude that bonds to his hoodie. To keep Arma safe, the resistance organization ARMS assigns Aki Murasame, a fighter carrying two Mecha-ude of her own, as his constant shadow. She has her own agenda, though: she is tracking a Snake-Type wielder who left many of her comrades in critical condition. Meanwhile, a shadowy corporation called the Kagami Group hunts for the legendary Trigger Arm, a Mecha-ude said to offer limitless power. When the group puts Aki's life in danger, Hikaru has to work with Arma and find the nerve to fight back.