David and Toshinori first met not long after Toshinori moved to California from Japan. A young scientist, David is rescued by Toshinori, along with several fellow scientists, from an explosion in their building. David makes note that Toshinori's outfit got tattered in the fray, and as a thanks, decided to study Toshinori to create a costume better suited for him. This costume ended up being the iconic 'Young Age' costume for All Might. From their, the two grew very close in their college days, and became hero team in California.
Toshinori eventually told David about his goal to become a Symbol of Peace for people to rely on. David then shared this message with a crowd in L.A. after the pair takes down villains, believing in Toshinori to achieve his goal. Sometime after this, Toshinori had to return to Japan, a fact that hurt David, and is shown in Two Heroes to still bother and upset him. David still continued to create costumes for Toshinori after he left the United States, being the only one to do so.
When David got married to an unknown woman, Toshinori attended his wedding, and remained very close to the Shield family, becoming like an uncle/second father to David's daughter Melissa, Melissa referring to him as 'Uncle Might'. David and Toshinori did their best to cheer up Melissa when it turned out she was born quirkless. Toshinori encouraged Melissa to become a support engineer like her father, telling her that 'your father is my hero'.
Despite being separated Toshinori and David kept in touch via email throughout the years, as well as fantasize about their past together several times, Toshinori telling David about his weakening state and injury from his first fight with All for One. Eventually, Melissa invited Toshinori to the I-Island Expo to surprise her father and introduces Toshinori to David as 'someone you love'. David and Toshinori are thrilled to see each other, and David quickly notices the steam coming off of Toshinori's muscled form, dismissing his daughter and assistant from the room to hide Toshinori's true form from being seen. David is shocked at the extent of the damage to Toshinori's body, and scans him to see his quirk levels. Fearing his friend's untimely downfall and what the world will be like without the Symbol of Peace, David hired actors to pretend to be villains to steal back the Quirk Amplification Device he and his assistant created, hoping it can help Toshinori gain back the strength of his quirk.
When David is captured by Wolfram, who turned out to be a real villain working with All for One to hurt David in order to get to Toshinori, Toshinori once again comes to his friend's rescue. Once he is defeated, David apologizes to Toshinori for causing so much trouble, admitting his fear of a world without the strong hero he knew Toshinori to be. However, he lets go of the past, recognizing that Izuku and Melissa will protect the world as the next generation of heroes.
DaveMight is a somewhat rare ship, due to David only featuring in the movie Two Heroes, which some circles of fans are unaware of. Those that are aware of David's existence very much so love the pairing, making it David's most popular ship, though it has some rivals in ToshInko and SirMight. A common headcanon among the fandom is that Toshinori and David were a couple or at least friends with benefits while they were young and living together in California. The two are often portrayed as having broken up when Toshinori needed to move back to California, leading to David getting married to someone else, but still having been in love with each other the whole time they were apart. Often times, this leads to them getting back together now that Toshinori is no longer a hero, and can have time for a real love life.
Certain sides of the fandom, however, portray Toshinori as being Melissa's father biologically through A/B/O dynamics, as Melissa herself highly resembles Toshinori more so than David, having the same hair and eye color as him. Others have Melissa becoming Toshinori's adopted daughter once he and David become a couple again.
- They not only refer to each other by their first names (a first-name basis implies closeness in Japan), but address each other by nicknames; Toshinori calls David ‘Dave’, David calls Toshinori ‘Toshi’.
- Although David was once married, Horikoshi notes that he drew David with a wedding ring so that fans didn't think he was divorced. This, combined with the lack of Melissa's mother in the film, as well as her starting to be missing in Melissa's collection of photos as she gets older, it's implied that David's wife has died, likely when Melissa was young.
- In the “bloopers” for the dub version of ‘Two Heroes’, Toshinori’s (English) voice actor, Christopher Sabat made many flirtatious comments towards- and about David. These included speaking to David like the two of them were breaking up, and moaning/groaning his name in a borderline sexual manner.
- Prior the release of ‘Two Heroes’ , a dubbed “romance” trailer was released by Funimation. It took clips from the movie, and arranged them to make the movie appear as if it were a romcom between Toshinori and David rather than action. Eijiro and Katsuki also made a (rather suspicious) appearance in this trailer.
- The concept of Toshinori’s bisexuality is not a foreign thing, sprouting from a mistranslation in the manga that implied a past romance to have occurred between Mirai and Toshinori. The interactions shared between David and Toshinori only furthered this concept.