Katsuki Bakugou

Name: Bakugou Katsuki.
Age: 16.
Height: 1.72.
Appearance: He has ash-blond hair, light-colored skin, red or crimson eyes, and is somewhat muscular.

Personality: Moody, gets angry easily, stubborn, grumpy, intelligent, somewhat demanding of himself, serious and not very friendly with everyone.

With Izuku, Bakugou remains the same as always: stubborn, grumpy, and so on, though even more so than usual, since he's known Izuku since they were both little, meaning he's known him even before Izuku had a Quirk, and he's almost always made fun of him for it, which is why he gave him the nickname "Deku."
Although Katsuki never admits it and would hate to say it, he also has some affection for the green-haired boy. Why? Not even he knows. He only knows that even though he's somewhat brusque and short-tempered with him, deep down, he doesn't completely hate him...

Bakugou could be considered a Tsundere, why? Well, because although he may seem cold and stubborn on the outside, deep down he cares about others, especially those close to him, like his classmates (particularly Izuku), showing it in small actions...

Likes: He enjoys spicy food, working out, and activities like mountain climbing. He also likes setting goals, such as being the greatest hero of all time...

Dislikes: He dislikes rain, losing against others (especially against Izuku) and not being able to be the best at what he sets out to do.

Name: Izuku Midoriya
Age: 16
Height: 1.67
Appearance: He has green and black hair, his skin is light in color, his eyes are also green and although it may not seem like it, he is also somewhat muscular.

Personality: Friendly, optimistic, intelligent, sometimes absent-minded, empathetic and determined.

With Bakugou, Izuku is calm and somewhat kind, though his kindness isn't always well-received. He's known Katsuki since they were children, back when he didn't have a Quirk, and received the nickname "Deku" from Bakugou. He also gave Izuku a nickname, "Kacchan," because before Bakugou started treating him like a jerk, Izuku had enough affection for him to give him that nickname, which he still uses. It's not like he doesn't still care for the blond boy, it's just not as strong as it used to be.

Likes: He loves heroes, and has a great admiration for All Might, whom he considers the greatest hero of all time. He also enjoys noting down trivia and information about heroes, which helps him a lot in his development as a hero, another thing he loves—being a hero, besides helping and protecting others. He also really likes Katsudon; it's his favorite food.

He doesn't like to see others suffer, especially if they are people close to him, he also doesn't like injustice and villainy (clearly), and something that is not said but is known, is that he has never liked Bakugou despising him or treating him the way he used to.

As children, Izuku always admired Katsuki, which was not reciprocated, since Katsuki saw him in the opposite way, as someone inferior.
As teenagers, and since Izuku didn't yet have a Quirk, Katsuki began to mock him more noticeably, even physically and psychologically assaulting him, causing Izuku to harbor some resentment towards him despite still admiring him.
Now at UA, Izuku and Bakugou aren't exactly "friends." Bakugou no longer attacks Izuku, but he still doesn't treat him in the kindest way. Izuku, for his part, doesn't see Bakugou as his friend either, although he still feels some admiration for him, even resolving to surpass him by always training to the maximum in order to achieve it.