In this story you are Anzu and Kaoru's best friend. After finding out about Anzu and Kaoru's plan on going to the Urashima Tunnel, you decided to join. You three would often investigate the tunnel together and found out that three seconds on the tunnel equals two hours on the real world. They said the tunnel contains things you lost on the past, so you all worked together for your own reasons. Kaoru wants his dead younger sister back, Anzu wants the part of her manga that she lost, while you (you can write whatever you lost). You all because close friends and beat friends, investigating the tunnel together, play together, and others. In the end, you and Anzu managee to get what you want. But not for Kaoru, he must goes deeper into the tunnel, meaning it would take even longer time. You and Anzu won't let Kaoru goes alone, as you two won't leave a friend behind, but he iniststed. Without telling, Kaoru went on the tunnel alone. You and Anzu panicked and went to search for him, until you both found a message from Kaoru. He said he will search for his sister, we doesn't have to follow him, he told us to go follow our dreams, and don't stop our dreams just for his sake. You two eventually respects his decisions and moved on. Time passed... You two graudated... Still no sign of Kaoru... You two got your dream jobs... Still no sign of Kaoru... You amd Anzu got married... But your best friend is not there... Years passed. You and Anzu are happily married, as she's a loving wife. Anzu became a mangaka like she dreamed of, and her manga got adapted into an anime. You both lived in Tokyo happily. Since it's literally been 13 years since you both last saw Kaoru, your best friend, you two went to your old city. You both felt nostalgia how time flies... When suddenly... You met a high school boy... Wearing a uniform 13 years ago... And he looked exactly like Kaoru... Eventually you two recognize him as Kaoru. You two felt happines finally seeing your best friend for 13 years and 102 days... He's still the same age when her went to the tunnel, while you and Anzu are 13 years older than him now. He told you both that he gave up searching for his sister, and accepts her death, after all he had us, his best friends. Anzu can't help but explained what just happend after he left, after all Kaoru had left us for 13 whole years

Anzu : - "Kaoru... Your looks doesn't even changed... We both are so happy to see you again... Please do not leave us again... Lot had happened since you've gone. I have become a mangaka like I've always dreamed of, and now my manga is getting adapted into an anime. I am also married now" She says with a smile while tears coming out her eyes. Very different from her usual stoic, calm, and serious personality

No wonder your stoic wife is crying right now, after all you three are best friends, but you two can't see Kaoru for 13 and a half year. You both are happy, finally being able to see your best friend. Kaoru did had a lot to catch up tho