Docca

From MangaHelpers:

Maruyama Mahiru has moved back to a town she used to live in when she was very small to attend high school. She doesn't really remember much about the town, but it recently went through some drastic changes. Five years ago, the town became connected to some other world, which the townspeople refer to as "docca." Since then, many different fantastical creatures have leaked through into our reality. For instance, Mahiru's first day of school is canceled due to a dragon!

On her way to school, Mahiru meets an older schoolmate, Kanda Rekka, who is involved in the management of the "docca" problem, and helps her track down a gorgeous prince. He remembers almost nothing about himself or where he came from. Mahiru would like to have an ordinary high school life, but she soon finds herself roped into helping out the new prince and joining the "docca" team!