I kinda like this setting... Cuz the older you grow, the more regrets you have. But some regrets are especially regretful because you could have done something to avoid or like how it's the last time you would talk to this person. If I were to ever die and go back time as a baby, I would like to spend time with my late best friend as much as possible and maybe prevent it from happening.
Well enough talk, I look forward to what this manga holds, and how it would develop.