Author Kohei Horikoshi‘s comment on the 34th complied volume of My Hero Academia released on May 2, 2022, revealed that he had planned to reveal Aoyama as the traitor originally in volumes 9-10 during the School Trip Arc.

Horikoshi’s comment translates as, “Originally, I planned to reveal that Aoyama was the traitor in the School training camp arc (Vol.9 – 10). That was a big change, right?”.

Twitter user Volk (@Volkerstime) presented an explanation for Horikoshi’s revelation in this volume. He stated that the author delayed the reveal of the traitor by twenty-five volumes to not disturb the sales count.

The Twitter user backed up his explanation with a screenshot of a roughly translated interview with Horikoshi conducted after the completion of the play My Hero Academia: The Ultra Stage – A Symbol of Peace.

In the interview, the author revealed that the sales for My Hero Academia dropped as soon as he hinted that villains will take the centre stage. Even though he had already planned the plot and he couldn’t let the villains walk away, Horikoshi decided to cut short some scenes during the summer training camp and rushed to the next battle.

My Hero Academia is a Japanese superhero manga series written and illustrated by Kōhei Horikoshi. The series has been serialized in Shueisha’s Weekly Shōnen Jump since July 2014, with its chapters additionally collected into 34 tankōbon volumes as of May 2022.

The series has also inspired numerous spin-off manga, such as My Hero Academia: Smash!!, My Hero Academia: Vigilantes and My Hero Academia: Team-Up Missions, as well as an anime television series by Bones.

Its first season aired in Japan from April to June 2016, followed by a second season from April to September 2017, then a third season from April to September 2018, a fourth season from October 2019 to April 2020, a fifth season from March to September 2021, and an upcoming sixth season.

It has also received three animated films, titled My Hero Academia: Two Heroes, My Hero Academia: Heroes Rising, and My Hero Academia: World Heroes’ Mission respectively. There are plans for a live-action film by Legendary Entertainment.

Both the manga and anime adaptation have received an overwhelming positive response from both critics and audiences, and are considered one of the best of the 2010s, with winning several awards including the 2019 Harvey Award for Best Manga. As of January 2022, the manga had over 65 million copies in circulation worldwide.

Source: Twitter(1, 2)