Friendship is by no means an uncommon theme in anime, but few recent anime have done as good a job at portraying a friendships that feel like, well, actual friendship than Konobi.
12 Days of Anime
[11] -konosuba: pettiness-
Not all small things are pretty. In fact, some are petty. Like Konosuba‘s Aqua.
[12] -introduction to small things-
A choice is made, and we follow the droplet of water until it reaches the puddle.
Mage in a Barrel 