I believe that he was 14 years old before the three-year time skip. That would make him 17 years old and below the legal threshold for marriage. It DOES NOT excuse this dim watt from noona-zoning his fiance. I guess he was put on the spot but he should have had enough time in the past three years to come up with a better explanation. Shouldn't have had the little tart in his apartment taking a shower in the first place. But as someone in the comments section said before ... how else are we going to get the part with the love triangle unless this misunderstanding happens. Unnecessary drama is unnecessary until the author paints himself in a corner and needs to pad the story so he can stretch it out some more.Actually, the legal age for marriage in S.Korea is 18 for males, and 16 for females, with parental consent, so technically they could get married right now!