It's the year 2046. Mikako Nagamine and Noboru Terao are middle school classmates, tentatively sharing an unspoken first love--but unbeknownst to him, Mikako has been recruited into the UN Space Force, and instead of going on to high school, will join the spacecraft Lysithea to search for alien Tarsians. As she travels further and further to the outer reaches of the solar system, the time it takes for a text message to reach the Earth grows longer and longer. Back on Earth, time passes normally for Noboru, but as the years pass he still can't forget the voice on the other side of the cell phone...
