Your face already has the shape of an adult's, one of my friends is a Chinese guy about 18 or 19 and his face looks just like that, though he's about 5'11" and broad-shouldered. You'd look a lot older if the shot was from a different angle, different body language, and a more mature facial expression.
Warning. Intense shota-ness (according to the FE4 Thread anyway. ) ahead.Spoiler -
Shit, you're pale as hell. Move your computer setup under a window, amigo.Spoiler -