This would be salvaged if it was a short story but:
1. The characters are really dumb, or shallow I guess. They say meaningless things and cry every other panel (so much so that crying isn't a significant event anymore)
2. I'm disappointed with the plot. Back when it started out there were plot mysteries regarding Umi's true feelings and thoughts and why her lifespan fluctuates. I had many expectations for complex character building, but all we got was some woke but non-substantial dialogue, lots of crying and lots of that same copy and paste smile Umi wears. All we got in the end, was some cliche bored god who is for some reason very cruel and Tarou very predictably strikes a deal with him, loses his memories, is recovering them etc.
Climax of the manga (solving Umi's lifespan) was also very anticlimactic and boring.
3. Maybe this manga would have been a lot more bearable if the characters weren't crying all the time, and if they didn't spew random quotes. The author really took this way too seriously, which if she didn't could have made it so much more bearable as a simple gag manga with some emotional moments.
Conclusion:
Had high expectations due to the meaningless suspense in the beginning, got shot down with shallow characters and bad storytelling.