Ring Ring: Eiyuu Kishi to Isekai no Otome  

In Japan three years ago, a student named Shiori looked after a knight that had been transported there from another world. Despite his successful return to his own realm, it was now Shiori's turn to be transported to an unknown location. With no one to depend on, she aimed to meet with the knight again, only to discover that in this new world he was considered a hero rather than just a knight.

Ring Ring: Eiyuu Kishi to Isekai no Otome began as a web novel on Shousetsuka ni Narou under the title "Ring Ring" (リングリング).