It is the year 2046, and teenage sweethearts Mikako and Noboru are hoping to pass all their exams and attend the same high school together. But Earth is fighting a war against the alien Tarsians, and when Mikako is selected to become a pilot, the young couple are separated, with their only means of communication reduced to mobile phone text messages.
As Mikako’s career takes her further and further from the Earth, her messages take longer and longer to arrive, and whilst the near timelessness of high speed space travel keeps Mikako young, back on Earth, Noboru is growing older. Can their love survive and transcend the ever growing distance between them?
In the mid twenty-first century, Earth faces its first real threat from space- the alien Tarsians. Against the backdrop of this interstellar war, however, some things remain the same- middle school sweethearts Noboru and Mikako spend every moment they can in each other’s company, and even hope that they can attend the same high school together. But, as fate would have it, that is not to be- for Mikako has been selected to become a pilot in the Tarsian war, and that will mean leaving both the Earth and Noboru behind.
And indeed, soon enough, Mikako is off to Mars to start training aboard the Earth ship Lysithea. But even as she learns how to pilot her combat robot, she finds the time to send a message to Noboru. With direct communications impossible, Mikako’s only option is to send text messages from her mobile, and by the time the first one reaches him, she will have completed her training on Mars and gone on to Jupiter.
Whilst Mikako takes in the sights of Jupiter, back on Earth, the seasons come and go. Noboru is now a high school student, his days filled with the same routines- only broken by the messages from Mikako. But the Lysithea is moving out beyond Pluto, and soon it will take up to half a year for her messages to reach him. Every day, the gap between them is growing wider- but still, every day, Noboru checks his mail in the hopes of receiving a new message from Mikako.
The Lysithea has moved beyond Pluto in search of the Tarsians, but Mikako cannot help hoping that they won’t find them, for then she can return to Earth and see Noboru again. Once again, however, fate intervenes when the Tarsian fleet is detected. Mikako finds herself in her first real combat, but despite battling bravely against the enemy forces, the Earth fleet decides to withdraw- to a point one light year away from Earth. With the Lysithea ready to warp out, it takes all of Mikako’s skills to return to the ship in time to go with them- and there is no time to send a message to Noboru.
With no clear way back to Earth, the fleet decides to make a warp jump in the opposite direction and follow the Tarsians to Sirius, some eight light years away. With 48 hours left before they jump, Mikako has time to compose one more message to Noboru, a message that will take over a year to reach him. By the time he gets it, they will be even further apart, and Mikako cannot help worrying that Noboru might start to forget about her.
On Earth, a year has passed, and Noboru has stopped waiting for mail from Mikako- after all, it has been a year since he last heard from her. But one day, to his surprise, he finally receives another message, explaining how much the gap between them has widened. Acknowledging the extent of their separation, Noboru admits to himself that he has to become a harder and stronger person in order to carry on. He does not want to forget about Mikako, but he doesn’t want his life to be just about waiting for her messages. In the timelessness of space, Mikako will stay young, but Noboru must grow up- and he is ready to do so, even if he must do it alone.
The Lysithea has made it to Sirius, making its crew the first ever humans to gaze at a whole new planetary system. The fourth planet, Agharta, is reminiscent of Earth, but instead of feeling welcoming it just reminds Mikako of the home she left behind. As she sends a message to Noboru, Mikako sees a vision of her younger self, who tells her although she has come far, she has the potential to go even further, seeing even more of what the universe has to offer. But Mikako’s mind is focused on the things she left behind on Earth- if she could choose, then she would want to go back to see Noboru one more time.
On Earth, it is the year 2056, and 24 year old Noboru is about to start armada duty. One day, however, he finally receives another message. Although most of the message is just noise, two sentences remain- a simple greeting to the 24 year old Noboru from the 15 year old Mikako. And, although 24 year old Noboru is spending some quiet time on Earth, and 15 year old Mikako is engaged in furious combat with the Tarsians on Agharta, for a moment their minds are as one. Can thoughts transcend time and space, can a connection remain even between two people who are so far apart? If only a single thought can get through, what should it be? Perhaps, all that is sufficient is the simplest statement of all- “I am here”…