Itthoma

Itthoma is the slash ship between Arataki Itto and Thoma from Genshin Impact fandom.

Canon
Prior to the Irodori Festival, while neither had met in person, their voicelines indicate they had at least heard about the other. Thoma seemed fascinated by Itto and his Youkai heritage, and expressed the wish to befriend him. Itto, conversely, was chagrined that Thoma had been chosen for the Vision Hunt Ceremony and demanded to know what made him important enough to be chosen.

In addition, Itto is canonly friends with Ayato Kamisato, one of Thoma's bosses and close friends, which implies Thoma likely heard about Itto through that channel.

The Irodori Festival
Kimura was worried that some group was hogging the photo board during the festival and the guards were asked to not interfere. The Traveler accepted the request to check the board, only to find the Arataki Gang trying to enjoy the festival by having to spend no money on something special there.

Their leader, Itto demanded the Traveler have a competition in order to make them leave the board. The passing Thoma greeted the group and suggested they do a volunteering competition where they'd help whomever in trouble in the area. At first, Itto is not interested, but after knowing the prize is a special limited Rainbow Aster that he wanted, he accepted the deal and got to work. By the instant chemistry the two had, Paimon commented that the two seemed to be developing "a real bromance."

Unbeknownst to the Oni, the Traveler just got word on their last request that the prize drink contained soybean milk. And just when Itto drunk to the last drop, he crumpled to the ground due to his bean allergies, prompting both Thoma and Itto's gang to escort him to the doctor, much to the profuse apologies of the former who didn't know about Itto's bean allergy prior.

The Almighty Arataki Great and Glorious Drumalong Festival
While Thoma wasn't among those invited, the retainer nonetheless visited and commended the group on their efforts and even offered to help them out the next time the Gang wanted to host another event, offering to help with a venue, furnishings, and more that would all be negotiable. In addition, Thoma left Itto two King Onikabuto in a pricey container that implies the closeness he feels with Itto and knowing him enough to select a gift connected to one of Itto's favorite hobbies: Onikabuto fighting.

Quotes
"Hmm... Word on the street is that he's quite a character — apparently, he even has youkai heritage. Have you met him? If you two are close, maybe you could introduce me sometime. It's good to make friends from all walks of life... youkai included!"

- Thoma, About: Arataki Itto

"Some of the boys have been telling me that he was the star of the show at the Vision Hunt Ceremony. I'm like — are you kidding me??? How come he gets his own special ceremony!? Was the hundredth Vision supposed to be, like, stronger than the other ninety-nine, or something? Pff, nah, it can't have been that, 'cause, uh, hello! They would've chosen me if that's what they were going for."

- Arataki Itto, About: Thoma

"Whoa, there's a serious bromance developing here."

- Paimon about Itto and Thoma's interaction, About That Time We Saved the Tanuki Photoboard

"Hey, bro! Haven't seen you since the Irodori Festival. I hope you're doing well. I didn't know you were gonna be hosting a huge festival — you sure kept that quiet! Nice work! If you ever wanna host another festival in the future, feel free to come and discuss it with me first. If you need a venue or furnishings or anything else, I'll see what I can do. Everything's negotiable! By the way, I know you like beetle fighting, and I remembered that I had a couple of King Onikabuto at home. I left them on the wooden box over there. Enjoy!"

- Thoma's message, Amakane Bulletin Board, The Almighty Arataki Great & Glorious Drumalong Festival

Fanon
Within the fandom itself, many are keen on the idea of Itto and Thoma being a classic friends-to-lovers romance with Itto often teaching Thoma how to unwind and relax, and sometimes embrace the wild side of life. On Thoma's end, many like taking note of Thoma's attentiveness and care for those he cares about and often depict him caring for Itto. Some see Thoma as a mom friend while Itto is more of a dad friend, which means the pair being shipped would make them the 'parents'. On yet another angle, some also like the notion of Itto intimidating Thoma in a flirtatious way due to him feeling challenged by Thoma having a stronger Vision, and playing out scenarios where Itto challenges Thoma, or corners him against a wall and proceeds to flirt that way.

Despite this, the two befriend each other almost instantly and have a generally good relationship with each other, which often leads to them being depicted as having an easy-going and comfortable romance with each other often filled with fun and attending events like festivals.

Sometimes, Itto's friendship with Ayato can come into play, which can lead to the odd interaction of Ayato fooling around with the pair and participating in TCG's and other childish games with them, like Onikabuto Battles.

Within the fandom itself, Itthoma is often rivaled by AyaItto and IttoGorou on Itto's end, while on Thoma's, it's rivaled by ThomaTo. Currently, it has 160+ fanfictions on Ao3.

Fandom
FAN FICTION

TWITTER
 * Daily Itthoma Account
 * Daily Itthoma Account
 * Daily Itthoma Account

Trivia

 * Thoma was among the first characters to encounter Itto in-character in his Character Teaser, along with Ayato, appearing near the end where he witnessed Itto crashing a stage-play and telling Ayato to look backstage.