Migi and Dali are 13 year old orphan twins who have lived a sheltered life and have an unusual way of interacting with the world as a result. The story follows them as they try to solve the mystery of who killed their mother when they were 5 years old. From this, they have a view of the world as hostile, and I find it adorable to see them try to understand other people with the presumption that others are hostile and malicious. And then, once they find that others can be trusted, they come up against those who are hostile as they get closer to undercovering who killed their mother and why.
The story is full of twists and turns making you eager to watch the next episode. There is great character development, both in the twins themselves as well as their ability to see other characters as being multifaceted. At times there is some weirdness and things that are contrived, but it is forgivable since it is fitting with a story that is being told by children who are on the cusp of becoming more than just children. I find the animation is beautiful and the voice actors doing a superb job of bringing life to the show (I watched it in the original Japanese).
Additionally, I really enjoy the music for the opening and ending credits; I watch them in their entirety for every episode. It's such a fun show that it makes me sad that there are only 13 episodes. Honestly, one of the best animes I've seen this year and perhaps reaching on my top ten list of best anime series. I highly recommend.