The Little Bird Sleeps by the Sea (2016)

Blurb:
Left devastated after the tragic death of his parents and sister, Yuuichi Tachibana adopts his seven-year-old nephew, Ayumu. Seeking a new beginning, he chooses to move them to a new house with a view of the ocean, hoping for a peaceful setting where they can concentrate on their healing.

There they meet Ryou Kurebayashi, who owns a neighborhood deli, and become regular customers. As Ryou and Yuuichi grow closer, learning about each other’s unfortunately similarly tragic pasts, they begin to support one another – and Ayumu – day by day, building a little family of their own by the sea.

Source: www.anisearch.com/manga/39047