Episodes 4-6 of the Soukyuu no Fafner: Dead Aggressor - The Beyond series.

It is the year 2046, Noboru Terao and Mikako Nagamine are close friends who will soon be graduating junior high school. But after an alien attack on humanity, Mikako is selected for the UN military space expedition set to retaliate against the aliens. Separated, Noboru and Mikako attempt to keep in touch by sending emails to each other with their cell phones. Yet as the expedition journeys farther from Earth, the time it takes for them to transmit and receive each other's messages increases substantially. Hoshi no Koe revolves around the relationship between this couple as they try to stay connected despite the growing distance between them. [Written by MAL Rewrite]

In near-future Japan, Aya Okamura lives alone in an apartment away from her parents. Her mother has worked overseas ever since her childhood, so her aging father Kouji and their cat Mii-san are the only ones left in their family home. After a tiring day, Aya declines her father's invitation for dinner by lying that she is still at work. Yet that very night, she receives another call with sudden news that may bring this separated family closer. [Written by MAL Rewrite]