|Ugetsu Asari's Four Irregular Swords|
|Title||Ugetsu Asari's Four Irregular Swords|
|Weapon||Rain Flame Coated Swords|
|Manga Debut||Chapter 246|
|Anime Debut||Episode 170|
Ugetsu Asari's Four Irregular Swords form a set of swords consisting of one long sword and three short swords. This set of swords was used by the First Generation Vongola Guardian of the Rain Ring, Ugetsu Asari. It was said that Asari Ugetsu loved the flute, but when he heard that the Vongola Primo had encountered danger, he immediately sold off his treasured flute for this set of swords to aid him.
Through future Vongola technology, the 10th Generation Guardian, Yamamoto, uses a similar set of swords through the Cambio Forma of his Vongola Box Animal. The long sword which Yamamoto uses has the Roman Numeral I on it to symbolize the connection with the First Generation. What is different is that the short swords have blades made of rain flames (thus allowing variation of length) and can be used as propellants.
- Reborn refers to the long sword as a "nagakatana" in the anime, which is a term used to describe Japanese regular swords of extraordinary length in the 15th century.