Azami no Shiro no Majo

The last in a long line of Witches of the Black Wood, Marie Blackwood lives a quiet life in Edinburgh – away from the scrutiny of the Church. But when the Church thrusts 13-year-old Theo into her hands for safekeeping, Marie suddenly gains the responsibility not just of taking care of a teenager – but protecting the world, and Theo himself, from the amazing power that lives inside of him.
(Source: Titan Manga)