I thought she was his daughter in the first sight, but after looking for more details, I think she's his girlfriend.
In page 4, she acted kinda nervous beside him, that seems to be what a teenage couple would do.
In page 5, there was a panel of a flashback to their youth. That's the main reason.
So I guess he've been here every year in memory of her after she died for a long time
Edit: My mistake, that panel in page 5 isn't a flashback. We can still see his beard, I thought that's how he looked like in his youth. I guess both "girlfriend" and "daughter" make sense then.