Throughout her freshman year in high school, Mika Tahara (Yui Aragaki) loses her mobile phone, yet later discovers it in the school library with the help of an unidentified caller. Throughout the summertime, Mika and also the mysterious caller remain to interact, and agree to fulfill each other once college begins once more. The customer becomes Hiro (Haruma Miura), a delinquent-like child Mika is at first terrified of, who shows proof of his identification as the customer with a picture of the skies on his mobile phone.