So this needs some extra context that’s lost in translation. When addressing him, Douki-chan uses the term あなた (anata), which is *very* familiar language for this kind of situation. In some situations, it’s best translated as dear or honey, but other times, it’s just ‘you’. The catch is that even if it’s just ‘you’, it’s significantly more familiar than you would use for a workmate or acquaintance! If someone told me that, even without Valentine’s chocolates, I’d seriously thinking they have a thing for me. Yet, the closest translation in English is still the word ‘you’. We lose some of the context that makes this hit harder.
For Douki-chan, it’s probably the most forward she’s ever been in her life.
(There’s also the matter of あなたのこと vs あなた, but that’s a subtle difference. It’s kind of slightly emphasizes that it’s Douki-kun she’s waiting on? I don’t think I can give this explanation justice.)
