Years ago I read an interesting manga where the MC could see the number of lies a person said in his life. I found it interesting and after so long I sort of remembered it.
I am not really sure anymore but I think the manga is called Count 0 by Yuma Satoru. Kinda similar manga is Kimi ga Uso wo Tsuita (You told a lie.)
3.
Setting: Can be an AU without quirks or with them
After an accident something strange happens to Izuku. When he wakes up he sees numbers next to other people's head. It takes him a long time to find out what do the numbers even mean. At first he didn't understand why the number grew when he talked with someone (or when he sees others talking to each other - their number sometimes getting higher). When he sees his own number he gets even more curious, trying to find out what does it mean.
About the strange ability: When someone tells a lie the number next to their head gets bigger/higher. Izuku can see the number of lies a person said in his life (the numbers are either really high or -rarely- low.) It doesn't have to be a quirk.
It can be comedy or angst (or both :D ). If angst then it could contain Izuku finding out that his lover (for example wife-Ochako or an unimportant OC) has been cheating on him. Then lot of feels. Some comfort (maybe from an unexpected person). There are several possibilities for this.