@kaarme what you're not noticing is that the guy himself is the narrator, meaning only we know that he's right but he thinks he doesn't know hence the title " 'I' don't know" instead of 'This random dude doesn't know'. Can't really explain it properly but that's what I think. 笑
Ngl, it's FMC's misdirection and identity as "someone whom i'm not sure what she's thinking" which is why MC believed that she really didn't know that she could go home together.