Just like Zettai Ryouiki 絶対領域 or Nekomimi 猫耳, twintails is another common moe element that is popular amongst fans. It is a hairstyle that where the back of the hair is parted in half and tied on each side of the head, allowing the “tails” to then dangle down to the shoulders.
Personally I think twintails look really nice, especially if they are swaying softly in the wind. Of course, there many been many popular characters that have been designed with twintails, but my favorite is definitely our virtual idol Hatsune Miku.
Interestingly, some of my other favorite twintails characters are also all tsunderes as well – Tohsaka Rin (Fate/Stay Night), Hiiragi Kagami (Lucky Star), and Aria Kanzaki (Hidan no Aria).