Seigi, a middle schooler with martial arts expertise, is compelled to shield the vulnerable. After coming to the aid of a homeless man against thugs, he receives a mysterious palm tattoo as a gift. Little does he know, this tattoo is a covert weapon in the ongoing rivalry between the USA and the Serinistan Kingdom. Seigi's world turns perilous when a formidable girl, also wielding this secret weapon, aggressively hunts him down to reclaim it. As he struggles to survive her relentless pursuit, Seigi must unlock the tattoo's potential before it's too late.