Seijo wa Tokku ni Shoukansareteiru. Nihon ni.

She was supposed to have been summoned as a saintess, but was thrown into a country called Japan. Rei Natsukawa, a.k.a. Alexandra Oriel, hides her magic power as she works for a small company in modern Japan. She just wants to live a happy, peaceful, and uneventful life, but obstacles come up and get in her way. This is the ordinary, yet not-so-ordinary story of a powerful mage.

(Source: Akita Shoten, translated)