A Very Small Mistake (Patreon)

To win the Holy Grail War, Rin was preparing a special spell meant to summon an exceptionally powerful hero from another era. Unfortunately, during the ceremony and its preparations, Shirou decided to drop by to treat her to yet another carefully cooked meal. This made Rin stumble halfway through her chant, interrupting the spell in mid-casting… which led to an unexpected result.

Fortunately, Saber was nearby and agreed to guard Rin while she prepared to form a new contract. Unfortunately… she fell asleep.