|Nickname:||Vongola Rain Swallow, Rondine di Pioggia|
The Vongola Rain Swallow is a Box Weapon used by Yamamoto and is half of the Vongola Rain Box. It has the power to emit Rain Flames that calm down the opponent's Dying Will Flame. In the battle against Nosaru , this effect was actually extinguishing his Flames during their fight. The Rain Flames can also be used as a form of camouflage, as seen when the Future Yamamoto used the Swallow to hide the entrance to the underground Vongola Headquarters when entering.
Kojirou has been upgraded after Yamamoto was given the Vongola Box. It can now Cambio Forma and be used to combine with the Shigure Kintoki . This forms a legendary blade that was used by the First Vongola Rain Guardian, the weapon that is said to wipe everything clean, the irregular quadruple blade Asari Ugetsu .The tranquilization of these Flames can be so powerful that the opponent's flame based attacks appear to be not moving at all, as shown in the rematch of Genkishi/Saru and Yamamoto during the Choice Battle.
Box Type: Animal
Personality : Friendly and sociable
Skills: Rushing, rain shield, downpouring, wave, pecking, changing form
- It is reconstructed Rain-element Swallow for Yamamoto's use only.
- Made from Vongola's newest technology.
- Its basic abilities are just like other normal Rain Swallow, but it unites with Yamamoto's Shigure Kintoki via Cambio Forma, and into a long sword that mimics the First Rain Guardian.
- Yamamoto named it Kojirou.
- This name supposedly comes from the name of a sword master who is very famous for 'Tsubame-Gaesi', a special sword skill.
Cambio Forma: Asari Ugetsu: When activated, Kojirou fuses with the Shigure Kintoki to create a long sword and Jirou provides three short swords.