Premieres April 7th. The new PV is here. Check out the ANN article for additional cast/staff information. Synopsis from AniList:

The story of Jii-san Baa-san Wakagaeru follows Shouzou and Ine, an elderly couple who are living a quiet life in a farming village in Aomori Prefecture. After eating a mysterious apple that they discover on their apple farm, Shozo and Ine spontaneously regain their youth, but even after being reinvigorated they continue to live life at a grandparent-ly pace.