I’ve been told that if you slurp it you mix more oxygen into the tea to enhance the flavour. This is one place where you have to trade manners off against taste. Do we praise refined sippers for their ascetic prioritisation of appearance over pleasure, or blunt slurpers for their healthy disdain for pretense? I’m a slurper – in private – myself. Given that she’s using a teacup rather than a mug, and drinking at something like a garden party, Yoshika’s probably better off sticking her little finger out and sipping – unless she wants to stick her middle finger up at the Establishment!
(Having taken the tea into your mouth you’ve a choice: taste it at the front before shunting it to the back of your mouth, so that you get the lighter aspect of its taste followed by the bitter aspect, or attempt to hit all of your tongue with the tea at roughly the same time, so as to take both aspects at once.)