Denki has relatively short orangery-blond hair, parted to the right with a black lightning-shaped streak on the left of his side fringe, which is angled so that it partially obscures his left eye. He has slanted, somewhat triangular yellow eyes, and notably small eyebrows. He's a little skinnier than most of the other male students in his class, not having much visible muscle mass. He wears the normal U.A. uniform during school hours, the second button of his blazer undone.
In his original hero , he wears a plain white shirt, over which he wears an open black jacket with a white lightning pattern across his back, and matching pants with two lines running down his legs. He has a single, square-shaped earphone over his right ear, something resembling a radio antenna sticking out of the top. His updated hero costume consists of a slightly shorter black jacket with fewer white patterns, only two near the hem and collar, and a yellow rimmed lightning bolt going around each of his shoulders. He still wears matching black pants, but they only have a small zig-zag near each of their cuffs, and he wears a belt and a white v-neck shirt. Around his right wrist, he wears a wristband with a circular mechanism from which he can shoot disc-shaped Pointers which aid him in aiming his Quirk, and he wears a headset with a blue-tinted visor.
Denki is a friendly, social and energetic boy who likes to hang out with people. He is rather casual when interacting with others, including antagonistic figures like Denki may come off as blunt and reckless at times, but is always well-meaning.
Denki is somewhat flirtatious towards the girls of his class (and even the ones from other classes), often accompanying on their schemes and trying to pass himself off as a smooth talker. He is not very lucky with his approaches though, frequently having his advances ignored or outright rejected by everyone he asks out. He is also slightly mischievous, joining in pranks occasionally. Overall, it seems that Denki has an interest in appearing cool and trendy in order to impress people, but has a shallow understanding of how to do so properly. As such, he gets easily influenced by what's popular or stylish at the moment.
Denki is not very academically bright, requiring help when it comes to studying due to his constant neglect of school duties. He does not appear to show much interest in classes, gets easily bored from lectures and suffers anxiety attacks when dealing with tests. Despite this, Denki can show surprising knowledge about certain areas such as literature, art and music, possessing a large vocabulary that shows up every now and then. His overall lack of wit and tact often results in Denki looking like a fool in front of others, making him a common victim of snark, in particular from Kyoka.
Denki becomes quickly distraught when put into stressful situations. During combat situations, he is very quick to panic, leading him to accidentally activate his Quirk in the face of any imminent danger and leaving himself vulnerable in the process. He becomes more reluctant to use his full power when there are allies close to him, being afraid of hurting them through collateral damage from his volatile bolts. When he is assured that all his allies will be safe from his powers, he becomes more confident in his fighting abilities. He does not tolerate others looking down on him or his classmates and will defend them if necessary.
Whenever Denki exceeds his wattage limit, he loses his ability to discharge energy, with his entire personality changing into that of a giggling idiot for a certain period until he reverts back to normal. In this state, he is always giving thumbs ups, as a way to let others know that he is fine.
