The reactions of pro heroes to Deku fanfiction could vary greatly. Pro heroes who are more outgoing and friendly, like Mirio, might actively seek out Deku fanfiction just for fun. He could be the type to laugh out loud at the creative and sometimes wacky ideas in the fanfiction. However, more serious pro heroes, such as Aizawa, might initially be skeptical about the whole concept of fanfiction. But if the fanfiction has some deep insights into Deku's character and his journey, Aizawa might start to respect it more.
The theme of the underdog and the idol is also common. Izuku is the underdog, and the female pro hero is someone he looks up to. Their relationship then blurs the line between admiration and love. For example, if it's with Mirko, Izuku admires her brash and fearless fighting style. As they interact more, their relationship can change from that of a fan - idol dynamic to a romantic one. There can also be a theme of sacrifice, where either Izuku or the female pro hero is willing to sacrifice for the other in a dangerous situation.
Some might feel honored. They see it as a form of recognition of their importance in Deku's story or in the overall My Hero Academia universe. For instance, Iida could see his friendship with Deku being explored in a fanfiction as a compliment to their real - life bond.
One great place to find such fanfiction is Archive of Our Own (AO3). Just search for 'izuku x female pro heroes' there and you'll get a bunch of stories. Some popular ones often involve Izuku paired with Uraraka in a more heroic - duo - turned - romantic setting. Another might be Izuku with Mt. Lady, where the height difference and power dynamics can create really interesting stories.
Toge Inumaki is important too. His special cursed speech ability makes him stand out. Also, the principal of the school, Masamichi Yaga, is likely to be important as he is in a position of authority and has an influence on Gojo and the other students. There could be other characters like the members of different clans that also play roles in the complex web of the story.