Here she is, the saint in Japan is a Manga/Manhwa/Manhua in english language, OFFICE WORKERS series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.nl fastest updating comic site. The Summary is

She was supposed to have been summoned as a saintess, but instead got thrown into a country called Japan. Alexandra Ollier, a.k.a. "Rei Natsukawa", hides her magical powers and works as an office worker for a small company in modern Japan. "As long as I can live peacefully and uneventfully, this is fine." says Rei, who faces many small troubles standing in the way of her lifestyle. Follow Rei Natsukawa, a mage possessing high level magical powers, and her seemingly ordinary — yet extraordinary — story. (Source: Young Champion)