Ao no Millennium

A girl named Chinami survives a boat accident twelve years prior and is left with a mark on her hand—bells that do not ring. Now attending high school, she encounters a teacher who also has the same mark. When someone discovers the mark, they attempt to keep the two apart, leading to an unexpected event that sends them 450 years into the past. The source also mentions two additional chapters and a one-shot titled "BLIND☆ACCESS."