
Yes. Time has passed. But even without the time skip their age gap really isn't that big. If an American freshman in high school started dating a senior in high school we would not find that weird. But that is exactly what their age gap is!!
The art style just makes things weird for this manga. He was 13 at he start of the story but they drew him to look younger in order to signify that his curse and how his family neglected him stunted his physical growth.

I mean.. a freshman and a senior is a lil weird but that’s because ones like not fully matured but i agree it’s not that big of a deal when he’s like grown up cause their mental state/like growth (?) is kinda the same
And also they did draw him super young in the beginning which probably threw a lot of people off
I read some people saying he's only 13 no he's not I mean they can be together they like 4 years apart I don't see a problem