I WISH they made spin-offs of all the characters here, they're ALL anime worthy. As said in my review of the full anime, all the side characters/couples are the typical tropes we see in most romance anime, and that's why I love them.
You have a couple where the male teases a lot and is openly romantic, while the female is a tsundere and blushes a lot.
Another couple where the guy is dependent (in a funny way), class clown, popular and the female SOMEHOW puts up with all of that and wears the pants in the relationship.
A more down-to-earth couple where the guy is a perfect boyfriend and gentleman and yet the female jokingly (I think and hope) doesn't acknowledge that they're together and is very chill and casual about everything (yet unsurprisingly makes a big deal out of things, ideal bi-polarity). (Though by how they spend their time together and some scenes, it's blatantly obvious they're in a relationship).
AND SAKURA. I would LOVE to see Sakura as a main character in an anime (if there's a character like her in one PLEASE recommend it to me) because she'd be the PERFECT MC in both a romance and comedy anime.
In other words, the specials are 100% worth watching and are also part of the main anime, right after the credits. I wish it was longer, but oh well. Completely recommend watching this if you don't want Tsuki ga Kirei to end so soon!