3rd POV:
It's been about a week since Inasa and Izuku passed their provisional exam and Izuku had come to a decision. He decided he was going to be telling Inasa about One For All for many reasons. One, Inasa was Izuku's best friend who has supported him through many things during the entire semester including some emotional breakdowns in their dorm room due to his past haunting his dreams. Two, Izuku believed it was his right to tell who he wanted to about One For All just as All Might has informed multiple people about the quirk. Izuku believed that he had the right to have his own set of guard keepers that would be supporting him. Izuku knew he had his mother and the Principal of Shiketsu as somewhat of his secret keepers but they weren't really his. They were more out of needing to tell them due to events that happened. As such, Izuku wanted someone he trusted and that was around his age that he could go to with anything that troubled his mind which included One For All.
That is how he found himself in Gran Torino's apartment talking to him about revealing the secret of the quirk to Inasa. Izuku wanted Gran Torino to know that he was planning to do this since All Might had told him to never tell anyone. Gran Torino agreed with Izuku and that it was his decision to tell who he wanted and Inasa was honestly the best person since he knew of Izuku and All Might's connection already and All Might's form. As such, cluing him in on the secrets of One For All and All For One was honestly a logical step since Inasa spends a lot of time with Izuku and could be targeted by the villain if All For One found out about Izuku being the 9th user.
Gran Torino did warn Izuku to call All Might and warn him first about it. As such, Izuku called All Might right then and there since the man should be on his lunch break. As the phone ranged, All Might answered. "Hello, Izuku is everything all right since you don't normally call during the day?" All Might asked and Izuku asked if he was somewhere private where he wouldn't be overheard and he said to give him a few minutes as he moved into a private location. "Okay, I am in a private location now. What's wrong?" All Might asked and Izuku took a deep breath in. "All Might, I talked it over with Gran Torino and I plan to tell Inasa about One For All," Izuku said and the line was silent before All Might spoke up. "I see, I honestly can't blame you with how much he knows already either." All Might stated and Izuku was confused. Izuku asked if he was okay with it since he had told Izuku to never tell anyone when he first got it. "I must admit, I shouldn't have said that. It ended up causing problems with Eraserhead since he didn't know about the quirk and honestly you deserve to have people you trust completely with the secret as well." All Might stated and Izuku thanked him. Izuku did ask if he could help arrange for the detective to come up to Shiketsu High School. "With the risk of a mole being in UA, we also need to take caution of a mole maybe being in Shiketsu High School as well. I trust Inasa but this way we can be 100% sure by having him confirm via the quirk he has no connections to villains or the League of Villains." Izuku stated and All Might agreed that it was a smart move and said he would see if the detective could go up there in the next few days. Izuku thanked him and soon the call ended after a few more things.
Several days later, Izuku greeted the Detective who had arrived at Shiketsu High School. "It's been a while Midoriya. How have you been?" he asked and Izuku said he was good and all, especially with obtaining his provisional license which the Detective congratulated him on. "Now, Toshi warned me about you telling Yorashi, Inasa about the secret and I am here to verify his trustworthiness. Correct?" the Detective asked and Izuku nodded his head. "I don't doubt him, I just want to be 100% safe in the event somehow he is being threatened by a villain organization or something. That MAN is powerful and all and could easily threaten people, so I want to be safe." Izuku stated and the Detective agreed that it was a safe bet. Soon they entered a room in the school and the Principal had Inasa called to the room. Inasa arrived to find the Principal, Izuku, and an unknown man in the room and he asked what was going on.
Izuku decided to speak up first. "Inasa, I want to clue you in on some secrets that are very important. I want you to know I trust you but I need to be safe and you will understand why if you are able to learn this secret at the end of this. This is Detective Naomasa who has a quirk called the lie detector which can tell him if you are telling the truth or not." Izuku said and Inasa nodded his head and understood why the man was there. "Hello, Yoarashi. I will be asking you a series of questions that will help us identify if you are working with villains, being threatened by villains, or are being threatened by others to leak information or anything else. Do you consent to move forward with these questions?" Detective Naomasa asked and Inasa looked at Izuku who had a serious expression on his face and then nodded his head.
The detective then started to ask all of the questions that he had prepared for this and slowly worked his way through them. He did not indicate to anyone if something was true or not because he didn't want to tip Inasa off if something came up as false. Soon, he came to an end and looked at Izuku. "He's clean and everything came back as true to my questions. We don't have to worry about All For One currently threatening Inasa right now. Do you want me to stay for the rest of the conversation?" the Detective asked and Izuku said it was fine and thanked the man. He nodded his head and said to call if he ever needed anything and that he didn't always have to go through All Might to get him to help out.
Soon it was just Izuku and Inasa in the room. "Sorry about that Inasa. The information I am going to tell you is limited to only a small amount of people since it could throw the world into chaos." Izuku stated and Inasa was confused about what was so important. Izuku then started to speak about the story of One For All and the job it has carried on for centuries. As Inasa listen he became more and more shocked at what he heard. "As you can likely guess, the reason I am telling you this is because I am the 9th user and I wanted you as one of my secret keepers since All Might who is the 8th user before I had his own people he trusted with the information," Izuku stated and Inasa was silent for a while as he put his head on the table. After a while, he looked up at Izuku and said he was full of passion which made Izuku laugh.
"Of course you would say I am full of passion... shouldn't have expected anything else out of you!" Izuku said while laughing. Inasa just smirked and then asked some questions. "So this All For One... he's alive isn't he..." Inasa asked and Izuku calmed down and nodded his head. "Yea... he is. He's already taken another shot at All Might due to the U.S.J. attack with the Nomu creatures they have been making. We assume All For One is injured like All Might but he is still very powerful due to his wide range of quirks so I need to be careful. I want to help in the next battle but I don't know if All Might will allow me to help even though I have my provisional license. But I got to keep pushing forward no matter what because if dad fails then I have to face that monster alone." Izuku stated and Inasa shook his head. "I refuse to let you go fight him alone Izuku. If you ever fight him then you better bring me along since we are more powerful together." Inasa stated and Izuku looked shocked but it turned into a smile as Izuku thanked his best friend. Indeed, Izuku wasn't alone in his fight and had his friend who would help him kick butt!