Aoi Uroko to Suna no Machi

Aoi Uroko to Suna no Machi summary:

After her normal, happy life shatters, Tokiko and her father move to a small seaside town to live with her grandmother as sixth grade starts. There, the sound of the waves brings back a distant memory from when she visited seven years ago, a memory of almost drowning in the sea and being saved by a merman. Are there really mermaids in that sea? Tokiko adjusts to her new life in the small town as she holds out hope of once more meeting the merman who saved her.