No date announced yet. The PV is here. This is being made by Kinema Citrus as part of their 15th anniversary as a studio. Check out the ANN article for additional cast/staff information. Synopsis from the article:

Goodbye, Lara tells a tale similar to Hans Christian Andersen’s The Little Mermaid. The story follows a mermaid who makes a forbidden wish to be loved by a human. Following her death, she is reborn 200 years later into modern-day Japan in Lake Biwa, where she learns to adjust in a human world. The setting of Lake Biwa is in Shiga prefecture of Japan, which is also where director Takushi Koide’s hometown is located.