Gokinjo JK Isezaki-san wa Isekaigaeri no Daiseijo

The manga centers on Matsunaga, a salaryman who one day sees Seina Isezaki, his high schooler neighbor, being accosted by a thug. When he rushes to protect her, he is stabbed in the process. As he lays on the ground accepting that he is dying, Seina begins to glow, and she uses a mysterious power to heal his wounds. In that instant, both of them are transported into a fantasy world. It is then that Seina reveals that she was once a saint in this world, and one day got transported to Matsunaga's world through unknown means, and it also meant that she lost her magic. But somehow, when she touches Matsunaga, she gets her powers back.

(Source: ANN)