ObiDei

The Couple

ObiDei (带迪 ObiDei) is the term used to refer to the romantic relationship between Obito Uchiha and Deidara.

Their Relationship

Deidara and "Tobi" (real name Obito) were partnered in the Akatsuki after Deidara's previous partner, Sasori was killed in battle by Sakura Haruno and his grandmother Chiyo [[1]]. It is implied that they knew each other from before, since they knew each other's names. Tobi finds Deidara's severed arm on the floor, thinking he's dead and that's the only body part of him that remained. However, when Deidara appears asking for his arm, Tobi celebrates that he is alive and well. After losing the Nine Tails, nearly getting killed and losing his arms, Deidara isn't in a good mood, and warns Tobi saying that "even Buddha lost his patience when insulted a third time". Tobi keeps talking and Deidara, as he doesn't have arms, tries to strangle him with his legs.

Deidara's dynamics with his new partner is different from when he was paired with Sasori, who was his senior in the organization. Now Deidara becomes the mentor and Tobi the rookie, referring to Deidara from that moment onwards with the honorific of "senpai". His attitude also turns more mature and strict.

At one point we see the two approaching a dango shop in which Obito gets excited and starts sprinting, even after claiming to be exhausted. After ordering and getting the food, Deidara tries to take a peek of Tobi's face, knowing that he'll have to lift his mask to eat. However, Tobi turns around, to Deidara's disappointment. Obito mocks Deidara's art and compares it to a small paper lantern, saying it's a rip-off. Deidara then uses an explosion to send him flying.

In a further episode, as the two are traveling Obito claims, "I'm a schoolgirl in love with her senpai!". He also says "I show you my butt but not my face". This is most likely just Obito's faked personality coming into play, though it is what started the slash for viewers. Afterwards Deidara ignores the gesture, and once Obito tries to start a conversation he tells him to "go away." The two have a small argument, Obito wanting to search for [three-tails]  with his partner and Deidara preferring to search alone. In the end the two seperate, much to Obito's dismay. 

In episode 112, Deidara and Obito are seen flying across a lake on two of Deidara's clay birds. As Deidara watches Obito attempt to capture the beast, he ends up having to interfere and help Obito as to not drown. Later he explains to Obito how he needs to have a cooler personality. Deidara smiles at the boy while they have the discussion. 

As it gets darker, they continue to soar across the lake. Deidara worries about Tobi being so quiet, and says he didn't mean for him to stop talking altogether, however Tobi was pretending to be asleep which ended up in him getting blasted across the lake. Tobi's mumbling while he is asleep can be interpreted as him pretending to have a wet dream to annoy Deidara. He says "just like that, and now a little bit lower..."

In chapter 357 of the manga titled [vs. Sasuke!!”], Obito assists Deidara in his attempt to kill [Uchiha]. Deidara congratulates his partner after doing a job correctly which pleases Obito. When Obito mistakes Deidara's death, he falls to the ground saying, "He may have been strict but he was a good partner." 

At the end, Deidara uses his C0 explosion which turns himself into an explosion while trying kill Sasuke. Deidara was prepared to kill himself and anything near, so before his death he whispers, "Sorry Tobi" since the explosion would presumably be his death as well. This shows that he did care about Obito even if it didn't show.

In the spinoff "Rock Lee's Springtime of Youth", Deidara and Tobi appear and befriend Team Gai. In one scene Deidara's eyes sparkle as Tobi compliments him. In another scene, Tobi tells the story of Tobiko, a woman that works in an office and that is clearly based on Tobi. Tobiko has a crush on a colleague named Daraday, whose appearance is based on Deidara. She keeps a picture of him in her drawer. Later, Zetsu helps Tobiko get a makeover as part of their plan to seduce Daraday.

Evidence

• They have a joint attack, combining Deidara's C2-Dragon with Tobi's Mogurakure no Jutsu, to bury Deidara's bomb and make a minefield.
• In the Naruto Online Videogame, Tobi has clay bombs made by Deidara in his pocket which he uses against his enemies.
• In that same Videogame, Tobi says "Senpai will like this" if you show him a bouquet of flowers.
• Tobi always refers to Deidara as "senpai".
• Deidara shows that he cares for Tobi's safety and tells him to stay back during his fight with Sasuke so he does not get injured.
• In that same fight, Tobi seemed to have information on Deidara's secret technique he made to defeat Itachi, something no one else knew about. Deidara shared with him the existence of C4-Garuda.
• Deidara's last words are "I'm sorry, Tobi".
• While Tobi seems to be endangering himself around the three-tails, Deidara sends a clay fish to distract the beast so Tobi can be saved. 
• Tobi seems to enjoy being around his partner and gets upset when rejected. 
• In chapter 30 of Ninja Pals Tobiko (a girl based on Tobi) is in love with Daraday (a guy based on Deidara)
• In chapter 27 of the rock manga he reads * even though Deidara preferred to spend more time with his teacher Sasori, Tobi / Obito always wanted to be close to him
• Obito's Akatsuki ring has the "玉" kanji on it, which means "orb". Deidara's Akatsuki ring has the "青" kanji on it. Together, both characters form the word "sapphire".