Toga and Dabi are childhood friends. They both ran away from their past. They act like siblings. Toga gets away with calling Dabi by his real name. Toga enjoys annoying Dabi. Dabi sees Toga as as an annoying younger sister. Toga sees Dabi as an older brother.

Toga: Touya-

Dabi: don't you dare

Toga: -Todoroki, Touya Todoroki

Dabi: Toga 💢

Toga: what are gonna do about it Touya

Dabi: I told you to stop calling me that

Toga: it's your name

Dabi: Touya Todoroki is dead. He died in a fire years ago. I'm Dabi

Toga: liar

Dabi: am not

Toga: Touya Todoroki is alive and he is right in front of me. Touya is you and you are Touya, not just Dabi

Dabi: ...why are you like this?

Toga: [shrugs]

Dabi: [sighs] whatever