Due to their differing roles in the series, with Denki being secondary to the main cast, and Mashirao being background, the two do not interact commonly. This lack of interaction is only added to when their stronger relations with others are brought to stand (Kyoka or Eijiro and Denki, Toru and Mashirao). However, Denki and Mashirao have proven to have a rather sweet friendship through moments seen in the background of the main series.
Denki is commonly seen holding, playing, and simply stroking the fur on Mashirao’s tail, especially in times of lecture (by Eraserhead when someone does something he dislikes), or simply, when he seems to be feeling bored. This implies that they’re either close enough friends for such contact, or Mashirao simply is a “chill” enough person to allow it. It seems to be the previous, however, due to their proven friendship.
During a training exercise, a few of the students place “wagers” on who they think will complete it first. Eijiro turns to Denki, and tells him he believes Hanta will be the victor. Denki thinks for a moment, before he replies, “Nah, I’ve got odds on Ojiro!” Another time, at the Training Camp, as the class takes advantage of the on-site hot spring. It’s seen Mashirao and Denki rather close to one another, laughing and smiling amongst themselves. After stretching, Denki splashes some water towards Mashirao, who laughs and splashes him back.
Due to the combination of their lack of interaction, and the shadows cast by either character’s more popular pairings with other characters, KamiOji is not too popular in the MHA/BNHA fandom. However, Denki’s liking towards Mashirao’s (especially his tail) was quick to draw attention from the observant, and those who enjoy the (popular) headcanon of the ever-hyper Denki with ADHD. Some also like the enouraging moments kaminari has had with ojiro. Some people like how their the only "normal" members of their class (alongside kirishima).
KamiOji has 120+ fics on AO3, putting it far above most ‘rare-pairs’.
- Denki and Mashirao are amongst the 4 blonds of Class 1-A.