|Manga Debut||Chapter 192|
|Anime Debut||Episode 115|
The Rain Tube is one of the Rain Boxes that comprises Gokudera's Sistema C.A.I. It is the Rain Flame ammunition for the Flame Arrow. It provides a coating of Rain Flames around the bursts of Storm Flames usually shot by the weapon. The Tranquility effect of the Rain Flames weakens enemy defenses, allowing the Storm Flames to inflict damage with their Disintegration factor.