Ok, so I just finished watching the entire series in a few hours. I have to say that I have never seen an anime or movie that has touched me in such a good way. Many aspects of the show really parallels things that happened in my life, so I was able to relate to this show. There are a lot of good life lessons this show gives us that we can take away and apply to our own lives. Love is not easy and there will always be obstacles in challenges in the way to try to "sabotage" what you have. Also, Friends are important and they show their importance in this anime, especially to, Kotaro, the main male character by being sort of like his guardian Angels...
Furthermore, this anime is very smart on how they portray things. The silence of the characters are done on purpose and the "sound effects" are used to let us know how they are feeling. The BGM and all vocal songs sang by Nao T. are also very well executed. She covered many old JPOP classics and made them her own and sang them all better then the originals. The drawings can be at times extremely simple and sometimes very scenic, both ways works. Most of the scenes they drew in the anime are in fact taken from 100% actual places in Japan that I want to visit one day.
Fortunately, or unfortunately..., this will be a tough one to top or even beat, if ever. If there was ever anime romance anime or even movie, I would probably compare them with this anime. They would either be better or not good enough compared to Tsuki ga Kirei. Definitely my top 3 favorite anime of all time and I'll be watching it over and over again because I enjoyed it that much!