Okay, that volume redeemed the series, at least for now - and it was getting sorely in need of it!
Basically this whole thing is a long flashback to Yamato and Kakeru as kids. Kakeru really shines when he's not his current wishy-washy self: it's easy to see what would've made little Yamato gradually fall for him, because Kakeru was such a fun, generous, brilliant light. He's actually...a lot like Yamato's dad, as it turns out. Very similar carefree but deeply caring personalities.
There was a lot of adorable stuff with their families, including Kakeru snapping at his pregnant mother for throwing away his trading cards, and then sobbing later because he didn't mean it and didn't want her to wind up in the hospital. (She was just having his younger twin siblings.) The part with Yamato spending spring break with Kakeru's grandparents was also fantastic, especially that late night conversation between the grandfather and Yamato under the stars - with the line about even forgotten memories becoming a part of who you are.
Yamato does end up recovering his memories from the day of his dad's accident, though...I'm not sure how his mother hadn't connected before that it was Yamato's birthday, or to think to check her husband's phone to find out what he'd been doing. (Taking photos of the cherry blossom trees and then having a video call with his son to apologize for not being there with him.)
Amazing scene: not seeing Yamato's father's face at all until the point when Yamato finally remembers the video call and the moment when he saw his dad smiling at him, shortly before his accident. That was built up so well.
I'm...completely astonished by the final chapter, where it turns out Yamato's father is alive, and presumably woke up from his coma some time earlier? Does that mean he'll be in the story more from now on?? I mean, I'm relieved it turned out that way, but it sure was some major drama and then a surprise reveal. At least he wasn't still in a coma a decade later, which was kind of where I was assuming it might go.
Honestly, this puts a lot of the things from the school trip in perspective...and makes Kakeru's actions even more frustrating. Yamato wanting to share a special place from his childhood with Kakeru, in his father's hometown, in a place he had specifically visited with his father when he was little, is so incredibly meaningful once you get all the backstory about his dad's coma and how Kakeru helped him through that really tough year.
It also makes the temporary amnesia after the kiss slightly less ridiculous...because Yamato has a history of his brain shutting out super important moments due to stress and trauma. Which, again, is something Kakeru would've known and makes it pretty terrible for him to have cut off his friendship with Yamato due to him not remembering something important.
Shouldn't he remember? How much Yamato had agonized and cried and hidden the fact that he couldn't recover those memories from the day of his dad's accident?
So I really enjoyed this volume, but it does make the rest of the series feel kind of...not all that well thought out.