Koufuu (a Touhou LW original) refers to a refreshing spring breeze on a sunny day or a wind that blows after the rain clears. This is an apt temperament for this Daiyousei, an exceptionally peaceful fairy. Daiyousei has maintained her super peaceful Wood Phase and Moon Essence temperament.

The ability of Daiyousei from the world with exceptionally big wars (a Touhou LW original). Like the other Daiyouseis, the details of her ability are shrouded in mystery. When fairies cause a disturbance, it's treated as nothing more than a sideshow. No matter how wild they get or how big they talk, they're never taken seriously. In this world, everyone knew that fairies couldn't cause incidents or resolve them. But they were forced to revise that assumption when they realized the fairy war wouldn't end. For the longest time, Daiyousei's ability and almost everything else about her was a mystery. She's often seen around the Misty Lake or accompanying Lily White. In fact, Daiyousei isn't even her real name. That's just the word used to describe a relatively strong type of fairy. If you wanted, you could also classify Cirno, the Three Fairies of Light, Clownpiece, and Eternity Larva as daiyousei. ...Fortunately, new true data has been discovered. It is now known that she can swim through mist. Perhaps the reason why she hangs out at the Misty Lake is because that's where she can make the most of her ability. Daiyousei isn't suspected of prolonging the 12.8th incident because of anything to do with her ability. It's her stance on and understanding of battles of bullets and Spell Cards that's to blame. When youkai cause incidents, they are perpetrated and resolved according to the Spell Cards Rules listed in the Bill for the Naming of Duels. However, some of these rules are self-contradictory. The duels are games taken seriously that challenge harmony yet also maintain it. Youkai attack humans, and humans exterminate youkai. But how much of this is serious, and how much of it is a game? How safe or dangerous is this? These rules are incredibly hard to navigate for someone who doesn't actively take part in these battles. It's easy to imagine that when the fairies started their war, they didn't have a full grasp of the rules they were supposed to be using. And if Daiyousei questioned Cirno, the Three Fairies of Light, or Lily White about this, their confused responses would've made her even more worried. Daiyousei probably felt she had to do everything she could to stop the fairy war before something terrible happened. It seems that Mother Nature... or rather the temperament that makes up Mother Nature, chose to assist this kind-hearted fairy. Daiyousei gained a bigger form to match this increase in magical power. Speaking of temperament, it's theorized that while this incident is numbered the 12.8th, it might actually come before the 10.5th incident on the timeline. Or maybe it depends on the parallel world. Either way, if that's true, it might help explain why temperament chose to assist Daiyousei.