The show is like a combination of Studio Ghibli's whimsical storytelling and Madoka Magica's artistic darkness. It subverts the story of adventure and reveals the dangers that lay in going to the abyss--the price to pay for going beyond. While the story isn't afraid of backing the characters against the wall, it does so with a sensibility. While at times dark, it never once strayed to angst territory. It showed what it takes to survive.
Riko and Reg are endearing leads who compliment each other in terms of character and abilities. I love them and hope for the best. Nanachi is also awesome and furry.
The main drawback is that the show isn't complete in terms of story. On the bright side, the story seems to be continuing so in due time I would finally see the characters' fate.
The art and soundtrack are awesome and brings in the tone of Made in Abyss. Overall, watch the show. It's worth it.
