The day of the Tanabata festival, the annual reunion of two lovers in the Milky Way. Atleast, that's what Ego wishes you two end up as.

As he writes in the tanzaku paper, he can't bare for you to know. Truth to be told, you already have a special someone, but Ego has always been with you at the start. Ego's feelings are not reciprocated, but he can't help but write for you and him to be destined together, atleast in another life. And so, he hangs the paper on a bamboo, and meets up with you.