Sontails

Sontails is the slash ship between Sonic and Tails from the Sonic the Hedgehog fandom.

Canon
In most canons, Sonic and Tails are best friends and sidekicks in most adventures, even both showing their brother-like relationship. Tails is considered as the closest friend to Sonic and his most trusted companion in the series. It is also said that Tails is the only person to be close to keeping up with Sonic's life style.

Games
They first time met in Sonic the Hedgehog 2 when Tails saw Sonic running like the wind made Tails impressed, admire him for how cool he was and then began to following him. Sonic eventually stopped and the two became close friends. He began to hang out around Sonic at all times of the day, catching up with him using his two tails.

Sonic and Tails were always there to help each other, their friendship growing until they had a more brotherly relationship. It is often that Tails invents machines for Sonic in his help.

In Sonic Rivals 2 it is shown that Sonic trains Tails to learn how to run and fight in their free time. Whenever Sonic has an adventure, he always comes to Tails and asks him to come along and Tails is always ready to help. Tails also used to depend on Sonic a lot, but later realized that he cannot depend on him forever. Sonic is also an idol to Tails, and Tails just wants to be as heroic as he is.

Despite his admiration of him, Tails can sometimes get impatient and annoyed by Sonic's fast-paced behavior and attitude. He downright hates when Sonic ignores him as seen in Sonic Adventure, and he gets annoyed when Sonic leaves him hanging when he runs off or when he is planning to do reckless things without much thinking. Despite facing such cases, though, Tails remains loyal to Sonic and stands by his side to aid him no matter what.

After Sonic and Tails crashed the Tornado on Lost Hex in Sonic Lost World, their friendship is put to the test when Sonic's arrogance places both of them in trouble and have little choice put to team up with Dr. Eggman in order to stop the Deadly Six. Tails was hurt that Sonic wants Eggman to turn off his life draining machine instead of him, along with the hedgehog scolding Tails for when his actions nearly got him hurt. When they came across a capsule in Silent Forest, believing that it is harmless Sonic goes to activate it, but just as he is about to Tails realizes that the capsule is a trap and pushes the blue hedgehog out of the way to save him, but ends up getting himself caught in the trap that was meant for his friend. Sonic felt terrible for want his actions had caused to Tails and made it his mission to fix his mistake by saving Tails from the Deadly Six. This has the grim Sonic attacking Zor out of rage. When Orbot asks Sonic if he can become his new sidekick, should they don't find Tails, Sonic turns him down before stating that he will find Tails, no matter the cost. The Deadly Six had originally planned to turn Sonic into a robotic slave, but since they have Tail instead they decide to follow through with their plan on him, luckily Tails manages to reprogram the machine to prevent his freewill from being taken away. Because Sonic wasn't away of this at the time, he was shocked by the sight of Tails' seemingly modified robotic slave form, until Tails attacks the Deadly while stating that he'll never harm his friend. Relived that Tails is still himself, the two make their way to turn off the Extractor, along with returning the stolen life energy back to their home world. Sonic apologizes for doubting Tails as they mend their friendship.

Adventures of Sonic the Hedgehog
They share a very close bond each other while Tails looks up to Sonic like an older brother, but also sees him as other members of a family, and wishes to run as fast as him.

Their relationship is portrayed with varying degrees, mostly like brothers, but also like parent and child (especially in the Sonic Says segments) with Sonic being more-or-less Tails' legal guardian. Sonic appears to know of this flaw and does his best to protect him, but his protection methods are often the reason why Tails gets kidnapped by Dr. Robotnik in the first place.

Sonic Boom
In the first episode "The Sidekick" of the TV series, its plot specializes in Sonic and Tails' brotherly relationship. Even though they have arguments, they still work together. The main reason why Sonic was looking for a new sidekick in the first episode was due to Tails getting hurt on his watch, and Sonic didn't want to wrick Tails' life or safety again.

Sonic Mania Adventures
In "Metal Mayhem", Sonic and Tails enter one of Dr. Eggman's lairs and Metal Sonic takes two of their Chaos Emeralds. After defeating Metal Sonic, they, alongside Mighty and Ray, witness Knuckles punching Metal and Eggman out of the lair. Sonic and Tails are seen eating chili dogs at the end of the episode, with the latter choking on his.

Sonic X
The two are shown to have a close bond in Sonic X.

Sonic the Hedgehog (film)
Tails appears in the mid-credits scene. It can be implied that Tails has met Sonic prior to the events of the movie. Along with it is the hint that he came to Earth in order to find the hedgehog.

Sonic and the Secret Rings

 * Sonic meets Tails' doppelgänger of the World of the Arabian Nights, when he saves him from evil spirits who were ganging up on him. To show Sonic his thanks, Ali Baba offers to help Sonic when he is in need of it.
 * When Sonic needed help to deal with the Ifrit Golem, he turns to Ali Baba who tells him about someone who can defeat it.
 * At the end of the game, Ali Baba aids Sonic on his next journey with Sinbad, as he helps Sonic to find away back to his home world.

Sonic and the Black Knight

 * When Sonic enters the smith shop of Tails' doppelgänger of the world of Camelot, he welcomes him. Afterwards he promise to aid Sonic whenever he stops by.

Fanon
Despite being less popular than Sonamy, Sonadow, Tailsmo, and Taiream due to the fandom's mainstream preferences, Sontails has a large fan-following which still extends to this very day.

Sonic and Tails have made it to many "Best Video Game Duo" lists together.

Fandom
FAN FICTION
 * Sonic/Tails tag on FanFiction.Net
 * Sonic the Werehog/Tails tag on FanFiction.Net
 * Tails/Sonic tag on FanFiction.Net
 * Tails/Sonic tag on FanFiction.Net

DEVIANTART

INSTAGRAM

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WIKIS
 * in

Trivia

 * When Sonic and Tails are paired up in Sonic Advance 3, the duo is known as Unbreakable Bond. It is one of the four pairs with special names.
 * Sonic and Tails appear together in all the canon continuities except Sonic Underground, which is the only canon Tails does not appear in.

Variations

 * Sontailsmo - the polyship between Sonic, Tails, and Cosmo
 * Team Sonic - the friendship including Knuckles the Echidna