If he is telling the truth, and Five is willing to trust him, it should come as a relief. His personal traumas aside, the things Mingyu saw could easily cause trouble for him if he's choosing to share a roof with the rest of them for the time being. He still stares for a while, looking for any tells that he knows more than he says. Fox at least doesn't seem like a good enough actor that he wouldn't be able to see the signs if he'd learned more.

That doesn't make it less strange that he found the tattoo and immediately assumed it was used on him. Unless he's seen that kind of reaction before and he was giving off signals. Either way, Five clearly doesn't look like someone who is used to being apologized to. He doesn't really know how to handle it.

"Do you want me to blame you?" That seems to be what he's getting at. Maybe he'd rather be responsible, but Five doesn't see the point. He's said he's sorry plenty of times to his family, and it never once made him feel less guilt for what he caused.