Summoning: Toad Mouth Bind

A peculiar technique of partial invocation that summons only an organ: the esophagus of a great, fire-breathing toad from, sending the enemy into his stomach. If activated inside a building or a cave, this trick can ensnare the enemy without them realizing it. In this interior, even the foothold is unreliable, the enemy finds themselves in a tight spot, having a hard time performing at their usual level of skill, and unable to find a proper response. The inside of the esophagus is highly flexible, and adhesive, and won't even allow liberty of movement. In time, the walls of flesh close in and envelop the enemy, dooming them to go inside the stomach where they will be digested.

Jiraiya could control the esophagus, causing it to expand, contract, or grow in whatever direction he wished. When first used, Jiraiya claimed that no one had ever escaped from this jutsu. Itachi Uchiha and Kisame Hoshigaki managed to escape when Itachi used Amaterasu to burn through the esophagus, which is said to be fire-resistant.

Trivia

 * In the video games, parts of the esophagus also spew fire, which fits with Jiraiya's description of the animal the toad esophagus originates from.