Nice story.
Two comments about the ending:
1. I think, after the boat scene, not only Yuu but also young Hanada returned to their respective times (Yuu returned to 2017, young Hanada returned to 2000) and lost their memories of all time travel stuff. This is why old Hanada had a son in chapter 2.
2. While Yuu was reading her mom's texts in the epilogue, there was another person beside him. Who is that?
1. I think, after the boat scene, not only Yuu but also young Hanada returned to their respective times (Yuu returned to 2017, young Hanada returned to 2000) and lost their memories of all time travel stuff. This is why old Hanada had a son in chapter 2.
2. While Yuu was reading her mom's texts in the epilogue, there was another person beside him. Who is that?