Good so far, interesting plot twist. The idea of time traveling is good but, how did she do it?? Maybe we learn it in the next chapters?
For now I'll just say that it's fun to read and I can feel the impact of their words and actions
Also I kinda relate to the last thing Akira thinks in the end of chapter 8...
Spoilers for Chapters 1 through 12ish with a hint of 15.
My guess based on context clues and Ruri and Pure's conversation is that:
In the original timeline, Pure and Akira met at a later time (college most likely). After dating for a time, they fell in love and got engaged to be married overseas. However, tragedy strikes (sounds like cancer but could be something else).
As she dies, Akira says that she wishes she could have known Pure in high school, so that they could have had more time together. Pure takes this idea and runs with it, somehow acquiring access to Ruri/Sumire's time machine, and leaping back half a dozen years into Akira's past. She then attempts to find her and rekindle their relationship. This is where Chapter 1 starts.
Worth noting that in this timeline, Ruri seems to act more decisively, perhaps spurred by his conversation with Pure. His actions and goals seem borderline insane, going so far to ask Akira "Don't you wish we had never been born?" He seems determined to ruin his parents' relationship before they fall in love, thus saving his mother from the heartbreak that leads to her death.
Some of this is guesswork. It is worth noting that Pure's memories get lost the further she alters things, so the most accurate things she says about the original timeline are right at the beginning when they meet. After that, she slowly starts thinking she was delusional and loses certainty in everything she's said (though she can remember saying it).
Got my hands on the last volume today and just finished rereading the whole series a few moments ago. I've never been particularly good at articulating my thoughts on stuff like this, so the only thing I'll say about the final volume is this. I'm happy to finally know how the series ends, after all these years.
Tbh, I found the final volume to be under expectations for what is otherwise a good manga. Creepy bro is front and center for half the chapters and the time travel explanation honestly takes more away from the main couple instead of adding on to their relationship and enhancing the story. It's a shame they spend most of the last volume introducing and trying to flesh out creepy bro and a whole new character to explain the whole time travel plot while leaving Pure and Akira on the back burner and then just use the last chapter for a rushed cut to wedding day.
Still a decent read but I feels like it really botched the landing after a strong first two volumes.