Natsu e no Tunnel, Sayonara no Deguchi

Rumors of the Urashima Tunnel have circulated for years, a ghost story whispered among the town's youth. They speak of a place where the laws of space and time falter, where a single step forward can grant your deepest desire—but at a cost measured not in money, but in years of your own life. For Tono Kaoru, the legend is more than just idle chatter; it is a painful echo of a past he cannot let go. Still haunted by the accidental death of his younger sister Karen five years ago, Kaoru carries his grief like a weight that grows heavier with each passing season. Then, on a sleepless night, fate brings him to the mouth of a tunnel that matches the rumor exactly. As he stands there, paralyzed by the weight of what he might find inside, he is startled to discover he is not alone. Transfer student Anzu Hanaki has followed him, her reasons for doing so as enigmatic as the tunnel itself. She proposes a pact: together, they will investigate the tunnel's secrets and test its powers. But Anzu’s offer is not born of mere curiosity. Her quiet intensity and guarded eyes hint at a desire she keeps tightly concealed, and she makes it clear that her cooperation comes with a price. As Kaoru steps deeper into the tunnel's ominous glow, he must ask himself not only what he is willing to sacrifice to see Karen again, but also what Anzu truly intends to take from him once the experiments are over.