The Vents

The Vents are a strange location in TFR.

Description
A mysterious and bizarre series of seemingly endless metallic tunnels that exist outside of reality. The vents' "purpose" seems to be to connect the different worlds, dimensions and kakeras. They seem to work on a specific way whose pattern can be marked down, but it is unknown how.

Access to the vents seems limited to beings with powers and/or knowledge that lives beyond worlds, or in some cases freak accidents; Leon is able to enter due to being a Nipper while Dutch fails trying to follow him, Weedman smokes so much of his "special greens" that his clairvoyant powers bring it there, while Amami and Saihara seem to be either accidents or related to their abilities (ultimate adventurer and seeker of truth flippy shitter).

History
The vents are likely to have always existed.

Season 1
When trying to ambush his rival, Amami Rantaro enters a vent and disappears.

Season 2
Hagakure Yasuhiro smokes too much of his smart weed and ends in a place adjacent to the vents, the Diamond Realm.

Season 7
Escaping his pursuer Chris Redfield, Leon S. Kennedy tries to hide into a nearby vent at the suggestion of hastily-made business partner Dutch van der Linde, who later fails to find him in the seemingly-normal vents.

Intrigued by the strange feeling of the vents, Leon forsakes waiting for Dutch or Fred, and crawls forwards hoping they'll lead to his dream (Ada). After he exits the vents, he paradoxically finds himself on the hill of a peaceful mountain village, but the guardian deity of the village, "Tomitaker", notices his presence as an outsider of the world and brings him to his realm for a match.

After being knocked-out, the entity expelled Leon back into the vents, and he decides to take a different route through the vents, and ends up in an island's beach, a Rokkenjima from another world. Climbing up the stairs and reaching the mansion's entrance garden, he is greeted by the cheers of the spirit of "Kinzomas", Goldsmith Claus, who is ready to deliver presents to all the children of the world. Next to the presents is a neatly tied box of apple juice, which Leon rushes to take as Kinzo looks horrified and calls his loyal reindeer to save the children's toys.

Stealing the apple juice and hopping back into the vents, Leon drinks himself until he passes out, awakening only to wish to return home to Fred, and crawling into another of the unending paths of the vents. This time, he is in a strange, darkly lit school. He walks around searching for any students or the headmaster, when he hears someone following him into the classroom, and tries to grab his Red9 (that he forgot to bring) before the lights suddenly shut off. Leon awakens back in the locker room with Fred celebrating his return and setting up a party (with alcohol) while waiting for Ada to come greet Leon; but Leon knows Fred would never support his relationship with Ada nor gleefully give him free alcohol, and the illusion set up by the Viceprincipal breaks, who tries to take Leon's soul by his hands now.

Meanwhile, Saihara Shuichi of the Mystery Masters is tasked with searching for Leon, and instructed to enter the vent from where he disappeared. His trip lands him in a strange set of empty rooms, where he finds a single note of an apparent traveler decided to investigate the vents.

The next time Leon wakes up, he's in a jungle and his memories are all messed up, all he remembers is being in a mission with Krauser, no, someone slightly different than him, but... he remembers now Krauser is not his ally, and more than that... he said terribly things about Ada.

Saihara continues walking through the seemingly endless rooms in his search and finds another note, but this one instead is a previous page of the group.

Again and again, Leon is kicked out of worlds and returned to the vents, only to wander into another strange place. This time he's confronted with what he thinks is TFR's Raiden who is guarding a princess. Leon is sure she must be Ada, but "Raiden" won't allow him to get any closer to her. However, the princess turns out to not be Ada, and so Leon has no option but jump into the vents again.

Lost without an answer, Saihara just questions, questions everything about these vents, even questioning if an answer to those questions will ever be found. Suddenly, a voice calls out to him, which turns out to be the Amami Rantaro from the original world who got lost. During his long stay in the vents, he wisened up and wrote all his research into notes, which he accidentally lost and decided would be better to take with him before leaving. Amami tells Saihara where to go before trying to explain how the vents truly work, but a shot-put ball thrown into the vents by his self from the new world.

Saihara and Leon both arrive at the Diamond Realm at the same time, where they are greeted by Hagakure and told to perform a "training arc", producing two spirits known as the "Mystery Masters" (in some world at least) Manny Pardo and Adachi Tohru.