|Title||Cane di Pioggia ver. Vongola|
|Manga Debut||Chapter 240|
|Anime Debut||Episode 167|
Jirou is Yamamoto's exclusive Rain Vongola Box. It was created by remodeling a Rain-attribute dog Box Weapon and is imbued with the Vongola Family's latest technology. It provides support by carrying Yamamoto's three short swords. That being said, there is nothing to criticize about its basic performance and one can hold expectations about its future development. Jirou, along with Kojirou, is one of the two Box Animals that compose Yamamoto's Vongola Box.
Although it is able to handle the short swords that it carries around, Jirou has yet to engage in direct combat so not much is known about its fighting capacities.
- Ugetsu Asari's Four Irregular Swords - Three short swords with blades made completely of Rain Flames, those hit by those blades will receive the Tranquility properties of those Flames upon themselves. Still, Yamamoto use them mostly to perform high-speed movement and flight, much like how Tsuna does with the Flames of his gloves.
- It belongs to the Akita Inu breed.
- Jirou is the only Vongola Box Animal who can't perform Cambio Forma. However, because of Yamamoto's Vongola Gear, he is seen to have a Cambio Forma appearance and has since helped in creating the 12th Form of Shigure Soen Ryu: Sadachi: Kirisame.