On an equally joking note, you can actually read that one as a "Kanako is old" gag too, since she forgot the same thing happened before assuming this one takes place earlier in time.
You look like you're having fun, what are you writing?Ah! Now that you mention it, I don't!!A summer greeting card for my friend Hecatia♪No, that's a little?Do you know her address?Do you think she'll receive it like this?Weird T-shirtMail for youShe received itHecatia