With the amnesia/lying being the main plot, I thought the flashbacks were used well to show how their past relationship was and what Fumiya was hoping to return to.
I did feel they packed a good amount of emotions and depth into the first 5 episodes. I think ep 6 could have been 10 minutes longer to make the resolution more satisfying for me but I still saw what they were going for and I think they achieved what they wanted to with the memories come back scene and then confession.
Not a perfect series but I think it's pretty high up there for how the series kept the emotional stakes high even with relatively not a big action oriented plot. A birthday party goes awry and then it's a weird slice of life second chance romance.