Not so long ago, as the urban areas progressed in their development towards being an information society, there were many places in the mountainous area which kept the same olden feeling. Yoshitsugu was a visitor from 100 years in the future who came to the mountain village Akio-mura. He had been labelled as a failure in the ultra-competitive society in the future, so it was unknown how he was able to travel to the past, an opportunity open only to those with high social positions.

Yoshitsugu, a "naturally born child" in age of artificial birth, wandered about in the mountains in the dark in confusion. He followed a firefly, which led him to a young girl in a small lake. The girl Iroha took him into her home for the night. Afterwards, he was granted special permission to stay in the village and enjoy life in the village for a little while. He got to know Iroha better, along with the actual visitors from the future, sisters Arika and Yuno, as well as the village chief’s daughter, Kotobuki. It was much different than the time he lived in: he felt soothed by the slow and carefree days.

Was it luck that brought him to the past? He thought that even he would be able to accomplish something here, like maybe fall in love with a girl. Their summer love story begins here.