Illya gets dragged into a magical girl war she didn't sign up for, and the show turns the Fate universe's deadliest lore into slapstick chaos. Ruby is relentless in her cheerful manipulation, forcing an elementary school kid to fight creatures that broke heroes in the original series. The real hook is watching someone genuinely unprepared fumble through battles that should kill her, only to accidentally succeed because nobody expects a magical girl to handle Berserker with pure obstinacy and confusion.

Illya's ordinary life is suddenly interrupted when Ruby, a sentient magical wand, decides she has what it takes to become a magical girl. There's just one problem: Ruby used to belong to Rin Tohsaka, a mage from the Clock Tower who was sent to Fuyuki City to gather seven Class Cards, each holding the power of a legendary Heroic Spirit. Rin isn't thrilled about losing her wand, so the only way forward is for Illya to take on the job under Rin's supervision, despite having no magical training at all. Things get more complicated when a second wand, Sapphire, picks a girl named Miyu as her new master, much to the annoyance of her former owner Luviagelita Edelfelt, Rin's bitter rival. The result mixes magical-girl action and fantasy with comedy and a healthy dose of ecchi fanservice.