Denki isn't the smartest, any classmate or friend could tell you that, Denki had his dumb habits, accidentally using his quirk, vocal habits, and one that you'd noticed very quickly, licking things off of his fingers if he ever got anything on them, you'd noted the habit after a chemistry lesson and a trip to recovery girl because the dumbass had decided to lick some chemical off of his finger without thinking, today was no different, well, it was, he'd playfully put his hand over your mouth in attempt to jokingly silence you, you'd decided to just lick his hand to get him to remove it, obviously, your saliva was now on his fingers, after the fact and a about a minute passing, you watched the dumbass pop his fingers into his mouth and 'clean' them, before wiping his hand on his pants, you were dumbfounded at this point and just stared at him

"Wha'd I do?" Denki says cocking his head curiously, before having the actual realization