Where can I watch Goodbye Robin! in United States?

As he looks at a flower, Mika is reminded of his childhood, and feels a creature awaken inside his head: a giant stuck in apathy. Also coming awake is another creature, full of wonder: Kai. Trapped inside the giant, Kai discovers countless memory bubbles and starts collecting them. With their help, she guides the giant through releasing his emotions – and Mika through finally accepting the loss of his childhood friend.