Chapter 121

Second Semester Opening Ceremony is the one hundredth and twenty first chapter of Kohei Horikoshi's Boku no Hero Academia Manga.

Summary
All Might regrets having brought the secret of One For All upon Katsuki and apologizes. All Might decides to properly explain to Katsuki about everything regarding One For All. And so, All Might spoke to Katsuki about One For All being a transferable Quirk that is passed down from generation to generation in order to fight evil, how he became the Symbol of Peace using One For All, the injury that limited him to using One For All and how he chose Izuku as his successor. After hearing the truth about One For All from All Might, Katsuki chastises Izuku for blabbering about One For All. All Might tells Katsuki that using up all his power against All For One was his choice and he doesn't need to bear any responsibility. Having heard everything, Katsuki decides that he is going to rise higher than Izuku as a Hero; Izuku accepts Katsuki's challenge and will rise higher than him. As Izuku and Katsuki argue about them rising higher than one another, All Might is happy to see that Izuku and Katsuki have become proper, true rivals. The secret of One For All has become a secret amongst All Might, Izuku and Katsuki.

Afterwards, Shouta Aizawa helps bandage Izuku and Katsuki's wounds and then proceeds to wrap them up using his weaponized cloth as punishment for fighting. It is revealed that All Might was the one who stopped Shouta from interfering with Izuku and Katsuki's fight after telling him that he would handle them and would bring them to him afterwards. After All Might tells Shouta that the fight was brought about due to Katsuki feeling guilty about his retirement, Shouta still refuses to let Izuku and Katsuki's transgression of fighting go by and will give an appropriate punishment after finding out who started the fight first. Katsuki says that he threw the first punch while Izuku retaliated. Shouta punishes Izuku and Katsuki by by placing them under house arrest; Izuku three days and Katsuki four days. During their house arrest, Shouta states that they will be cleaning the dormitory common spaces day and night and they must write a written statement of regret. Shouta tells them that if their injuries do not heal they must go to the infirmary and they mustn't dare think about relying on Recovery Girl. Having criticized them enough, Shouta tells them to go to bed.

The next day, Class 1-A learn about Izuku and Katsuki's fight. As Izuku and Katsuki clean the dormitory. Ochako hopes that they made up, to which Izuku replies that their reconciliation is hard to put into words; Tenya is happy that they got off the hook with house arrest only and that the rest of Class 1-A will attend the opening ceremony without them. Shouto asks Katsuki what he plans to do about the Provisional Hero License Supplementary lessons, to which Katsuki tells him that its none of his business. As they clean, Katsuki talks to Izuku about his One For All Shoot Style, telling Izuku that his wind up motions are too big and isn't useful in a slug-fest and neither does it mix well with punches. Izuku is glad about the information he gave about his One For All Shoot Style.

Outside, Tenya tells Class 1-A to not break formation. While on their way, Neito Monoma criticizes Class 1-A for having two of their classmates fail. Eijirou wonders if any of Class 1-B failed, to which Neito laughs. Neito reveals that all of Class 1-B passed and none of them failed Class 1-B are happy that they have pulled ahead. Shouto apologizes for letting Class 1-A down, but Eijirou tells Shouto not to let it bother him.Pony Tsutonori informs Class 1-A that according to Blood King, during the Second Semester Class 1-A and 1-B will be having a class together. Denki comments on Pony being a foreigner; Pony responds in a negative way, courtesy of Neito's bad teaching, causing Itsuka to criticize Neito. Someone tells Class 1-A and 1-B to stop holding up the line; Tenya apologizes for doing so. The person is revealed to be Shinsou, the General Departments student who fought Izuku in the Sports Festival. As Shinsou passes by, Hanta comments in Shinsou being more serious.

All of U.A arrive at Ground Beta. Mr Principal introduces himself. After talking about his diet and lifestyle going out of sync, Mr Principal states that the reason for his lifestyle becoming inadequate is due to the incident that took during the summer break. Mr Principal talks about All Might's retirement and the negative effect it will have on society and the Department of Heroics will likely see the most striking affects. Mr Principal tells the Second and Third years that the Hero Internships that they are engaged with they must have an awareness of the crisis and conduct themselves accordingly. Mr Principal apologizes for bringing down the mood but the Heroes are dealing with the situation to the best of their abilities and he would like nothing more than to develop them into individuals who will take over their efforts. Mr Principal ends his speech by saying that whether they are in the Department of Heroics, Support, the General Department and even the staff of U.A, they must not forget that they are the successors to the Hero society.

After Mr Principal leaves the podium, All Might ponders about "successors". All Might thinks back to when Mr Principal made a suggestion to look for a successor at U.A and gave him the opportunity to look for a successor by taking up a teaching position at U.A. All Might looks into the crowd of U.A students while thinking about Mr Principal stating that there is someone who would surely be a fitting successor amongst the U.A students.