I spoil the anime here, so be warned.
This anime was the second one I've completed with my best friend. Together we cried so bad over it but the sheer beauty of it made us marvel. This is the first anime I've finished that's made me want it tattooed on my body directly after the last moments of the episode. I may be a bit generous about how I rate things, but to me, this is the first anime in a long time that has made me feel such powerful emotions.
The animation style is beautiful and unique. When I see the characters, I can figure out what anime they are from purely from the style. As an artist myself, this is important to me. But I also love the way the style shifts, how some parts glow with color and how some parts fill you with a sinking feeling. This is obviously necessary to the plot, with the harsh themes. The color breathes life, then sucks it away at a moment's notice. I hope to read the manga soon so I can see how the style is different and how they make the story feel the same without the use of color.
It also does well with these difficult subjects. Abuse and suicide are obviously brought up, but they are handled with care. Mental illness is a big part of my own life, and it feels well represented without being either idealized nor being a taboo subject. The way that the characters react feels very human, while still having the charm of animated characters. This may be partially because they're so young, about 4th grade, but it feels believable even in this sci-fi situation. Also, in the end, Chappy is okay. Very important for me.
I and my friend watched this over the course of two days. The first day, we watched four episodes. The second, the final two. Almost immediately after getting on our call to watch, we headed straight for those final two episodes. I measure most shows in weather or not I want to come back to them. I often take breaks to do other things in my life, and if I don't want to finish something, then I find it to be an anime I don't particularly enjoy. Takopi's Original Sin is one I just had to finish, not matter how much it will make me cry. I tend to avoid shows that make me sad or that I know are meant to be sad. This is my first exception to that rule that I've found. I feel this anime is a must watch for people who can handle themes of mental illness and suicide. Watching the decent of the main characters and then the overall redemption is heartbreakingly beautiful. I hope that I can come back to this anime again and watch it again. It certainly will be some time before I can rewatch it, due to the saddening nature, but it is something I could see myself watching over again. I would recommend this to any of my friend that I believe could handle it. Obviously, its not meant for everyone. People with traumatic pasts may find some material within to be very triggering, so be careful.