My Hero Academia explains why Izuku Midoriya is determined to save Tomura Shigaraki with the newest chapter of the series. During the fight against the full powered All For One versus the growing power of One For All within Izuku and Shigaraki, the two powers began to react with one another. Surprisingly despite all of the chaos Shigaraki had wreaked during the war, Izuku Midoriya's last vow to the villain at the end of it all was that he was going to save him. As it turns out, Izuku and Shigaraki formed a much deeper connection than expected thanks to their uniting powers.
The newest chapter of the series continues Izuku Midoriya's conversation with the previous vestiges within One For All. After Nana Shimura had asked whether or not he could actually kill Shigaraki for good, Izuku explained in Chapter 305 of the series that he actually saw a vision of Shigaraki's tragic past and wants to save that version of Shigaraki that once had his hope crushed by trauma.
As Shigaraki began to further meld with the All For One power, it was soon revealed that All For One himself had a venomous and parasitic relationship with Shigaraki's body. This not only continued to push Shigaraki and fuel his hatred, but Izuku wants to break through this outer shell. He reveals to the vestiges that he felt a little boy crying underneath all of Shigaraki's rage when their power had resonated with one another.
He's fought some villains in the past, but he regrets that they all had to come to blows. Because he did not understand what made those villains the way they were, and still had as much determination toward their respective goals as they did, he wonders whether or not he would have had to fight them if he did understand their motives back then.
It's not as if he sees Shigaraki in that same light because the villain has killed and hurt people close to him, but in his heart he believes that the true hope that All Might and One For All helped to develop has a bigger purpose than to simply kill. He doesn't know himself what he'll do when the time comes, but Izuku is resolute in his desire to save his greatest villain.
What do you think of Izuku's desire to save Shigaraki? Do you think something like this is even possible? How will My Hero Academia even end the fight between the two? Let us know your thoughts in the comments or you can even reach out to me directly about all things animated and other cool stuff @Valdezology on Twitter!