Meh, I still like it for the most part. Not necessarily outstanding but it's certainly not as bad as the impression I got from previous comments below. The story doesn't delve too much on the psychology aspect and more on the romance, which is fine with the execution that the author went for imo. I'm also not bothered by the art that much; it has enough emotional input for me to overlook some minor flaws.
Btw, I'd like to counter-argue that this is pretty much the opposite of Mou Ichido, Nando Demo.. Amnesia is the only thing these two titles have in common, everything else in between is as different as could be.
Mou Ichido went for comedy and smut, while the drama was just strutting along at first and naturally came out to the forefront later. This manga headed straight into heavy emotions and heartbreaks and sad revelations right away, and eventually worked its way into a more hopeful and optimistic view of the future by the end.
The amnesia trope also played different roles in each: for Mou Ichidou, it was to reaffirm the already strong bonds between the main characters (they were at the peak of happiness before the mishap striked), while in this one, it happened to give the characters a second chance to fix their cracking relationship (the huge fight was the cause of the accident).
Here, Sakai's negative mental thinking was the biggest obstacle in his romance and he needed to get over his insecurities if he seriously wanted to keep the relationship. Hence the role of the amnesia and temporary separation as healing glue. Meanwhile, the couple in Mou Ichido was experiencing too much smooth sailing, and the memory loss was a test, or a hurdle they needed to overcome to strengthen their love ultimately. Its role is completely different. Not as the remedy, but the virus.