This is a woman who tries to eat healthy is tempted by a younger girl to eat unhealthy but tasty food. So this is not erotic just because of the facial expressions, but because she succumbs to pleasure, so to speak. Runa is presented with an opportunity to feel good, tries to resist the temptation, then she caves in and does it anyway, which is the basic structure of smut.
The above isn't unheard of in gourmet manga, but this one does take it a few steps further. There's a brief moment of dubious consent when Ichika shoves a takoyaki into Runa's mouth without asking. The thought bubbles are full of suspicious lines like "If you cram that much in all at once, I won't be able to think straight" and "my hands are moving on their own". Finally there is a 'climax' (with an optional afterglow) shortly followed by embarrassment and regret.
I would say it's more funny than hot so far. but I won't complain if they make the jump to the other kind of pleasure.