Majo no Jouken

Saya lives a secret double life. In a school, she's a normal high school student, but she's also known by her client outside the school as Maria, the witch. You may think it's just her alias for doing business, but Saya and her brother do know magic and they must follow the certain set of rules or bad things will happen.

One of her job aside from predicting her client's faith is to make them happy, and secretly lessened their bad luck from something deadly serious into small bad luck. Her job, what she do and her second identity is a secret, if someone knows who she really is, she will either have to make that person become her own people, or she will lose her magical power.

(Source: MU)