WARNING: The following contains spoilers up to My Hero Academia #295 by Kohei Horikoshi, Caleb Cook and John Hunt, available now in English from Viz Media.
At long last, My Hero Academia seems to truly be concluding its War Arc, wherein the Paranormal Liberation Front faces off against the united full force of the heroes. This arc has lasted for almost a year now, and after a nonstop series of reveals – including Dabi's true identity as a Todoroki, Mirio's return, Bakugo's hero name and Mr. Compress's bloodline – the dust is settling on the battlefield. It's a welcome end considering that the slew of reveals in the past few chapters may have induced a sense of reveal fatigue for manga readers.
However, the story seems to have yet a few more reveals up its sleeve. In My Hero Academia #295, Deku unlocks a new Quirk from One For All. This will be the third known Quirk that he's inherited from One For All's previous wielders, after Blackwhip and Float.
This new Quirk first emerges after Deku witnesses Shoto get roasted head-on by Dabi's Cremation Quirk. Terrified that Shoto is dead or badly injured, he wildly looks about for his friend and is relieved to see he's okay (likely because Shoto's own Quirk naturally comes with a degree of fire resistance). It's then that Deku notices a painful stabbing sensation in his head. He realizes it's not just pain from battle injuries -- it's the uncontrolled awakening of his new Quirk: Danger Sense.
Deku reveals that Danger Sense was originally the Quirk of the fourth One For All wielder. In previous chapters, we learned that the fourth wielder resorted to living secluded in the woods as a consequence of his Quirk and that because of this, All Might was worried about the effect it would have on Deku. While no further details are confirmed, the fourth wielder probably secluded himself on account of suffering immense guilt from being aware of all the danger people were facing in his vicinity, yet being unable to save everyone.
All Might was right to worry about the impact this will have on Deku. Considering his tendency to go to extreme, almost suicidal lengths to save everyone from strangers he's just met to his archnemesis Shigaraki, Deku's personality is a bad match for this Quirk. He's obsessed with the idea of being the next Symbol of Peace, and now he's awakened a Quirk that will put that obsession into overdrive. The reliance on one man to be the Symbol of Peace was perhaps Japan's greatest mistake, and it seems this Quirk will set Deku further down the path of trying to save everyone himself.
But there is a silver lining. If Deku manages to learn from Danger Sense that he can't go it alone – and that he needs to trust the competence of his allies – then he won't repeat the same mistakes All Might did. That single difference would make him a better successor than the past wielders of One For All could hope for.