The Tunnel to Summer, the Exit of Goodbyes: Ultramarine (Manga) Vol. 4

"According to an urban legend, there is a tunnel where you can get anything you desire in exchange for your youth--the Urashima Tunnel. Kaoru and Anzu take advantage of their summer break to launch an in-depth investigation of the tunnel, with disappointing results. Kaoru is about to head home when Anzu suddenly invites him to her place. Kaoru's nervous, and Anzu finally tries to express her feelings: "T-Tono-kun, I..."--