The Tunnel to Summer, the Exit of Goodbye

Kaoru Tono encounters a rumor about the Urashima Tunnel, claiming it can grant one's heart's desire but at the cost of years of one's life. When Kaoru discovers a tunnel matching the description, he is reminded of his late sister Karen, whose memory still haunts him five years after her accident. Anzu Hanashiro, a transfer student, becomes involved in Kaoru's attempt to explore the tunnel, but her intentions remain unclear.