WARNING: The following contains spoilers for for My Hero Academia Episode 69, "An Unpleasant Talk."
Over the past several episodes, we have learned much about Overhaul, the yakuza crime lord determined to take advantage of the power vacuum left in the wake of All Might's retirement and All-For-One's defeat. He has weaseled his way into the League of Villains, and spread a toxin that negates Quirks.
His increased presence in the criminal underworld has drawn the attention of Sir Nighteye, All Might's former sidekick, now the head of a major superhero agency and the man in charge of Midoriya's work-study program. With the other three work=study program students -- Uraraka, Tsuyu and Kirishima -- dragged into the fold of the Overhaul investigation, things heat up in this episode, all in a single, significant talk.
The episode opens with Midoriya and friends going to a huge meeting with literally every other major hero. That immediately tips off Midoriya that something big is going to happen. This is when Nighteye confirms the meeting is designed to share the information gathered over the course of the past few episodes about the schemes of Overhaul and his gang.
Most notably, Sir Nighteye confirms that Overhaul's yakuza have been contacting smaller gangs, before reaching out to the League of Villains (that began in Season 3, continuing to the beginning of Season 4). That leads to the Fat Gum sharing information about Overhaul's temporary Quirk-erasing ability -- though, as Eraserhead clarifies, it functions differently than his own Quirk. Eraserhead suppresses Quirks, while Overhaul's weapon injures the Quirk genes.
When Fat Gum investigated the dart, however, they learned something: The needle was laced with human blood. That means the Quirk-erasing dart is developed from another person's Quirk. And, as Sir Nighteye confirms, Overhaul's ability allows him to break down Quirks, such as create a dart. They then acknowledge that Overhaul's daughter, Eri, had bandages on her arm, which leads many of the heroes to theorize that Overhaul is ripping and twisting her body around into the darts.
This, very obviously, horrifies Midoriya and Togata, who had a chance to save Eri. They then vow to rescue the girl from Overhaul.
Sir Nighteye unveils his plan. He presents a map of Japan, outlining areas of strategic significance where the gangs are circulating the drug. While many -- like Fat Gum -- want to go straight to Overhaul to save Eri, others, like Gran Torino and Nighteye, think it's dangerous to strike directly: With the drug so widely distributed, they'd essentially have to go through an army to get there. Additionally, the attack could backfire, and provide Overhaul with a platform to recruit more criminals.
Many, including Eraserhead, suggest Sir Nighteye use his powers to foresee what's coming, but a few issues come up: Nighteye's Quirk is limited to one person per day, and he refuses to tell them if they will die, perhaps due to the trauma of what happened with Overhaul.
The meeting leaves the students troubled, leading Eraserhead to meet up with them, and admit that he wants to suspend the work-study program due to how dangerous it is. On top of that, he isn't sure he can trust Midoriya not do something reckless. But he also tries to acknowledge that Midoriya needs to not guilt himself over not saving Eri that last time, knowing that it will eat away at him.
Meanwhile, Gran Torino admits he encouraged Midoriya to train under Nighteye in order to help mend the relationship between him and All Might. As a result, Nighteye admits he sees a great deal of All Might in Midoriya.