Emotional storm clouds come between two unicorn friends.Harking back to Not Quite Narwhal (2017) in both cast and tone, Sima offers a friendship tale in which Kelp's close and aptly named pal Nimbus acquires a dark little cloud that rains when she feels down. The more she tries to ignore it or bottle it up, the bigger it gets…until it finally breaks out in a storm that sends her fleeing all company to huddle alone in a gloomy forest. There, she discovers that recognizing and getting to know the cloud actually makes it shrink-and just as she's feeling a bit better, Kelp gallops into view, which sets the stage for a joyful reunion depicted in the sweet, softly hued illustrations with an exuberant rainbow swirl. Kelp, who turns out to be "a very good listener," acknowledges the cloud matter-of-factly, and Nimbus comes to understand that though she may have up days and down days to come, weathering the latter with an accepting friend will make them easier. If some young readers subject to or familiar with similar storms (or a bit foggy on what a metaphor is) need explanation or discussion about depression to clear the air, the comforting message nonetheless shines brightly. (This book was reviewed digitally.)Weathers heavy themes with breezy sensitivity…and unicorns! (Picture book. 5-7)