...he wants to impress Haru. That's the thought that occurs to him, as he reads over the stuff he wrote earlier. Which, like, duh, obviously.
But that's the thing, when Haru "rejected" him, that felt like he was failing to be impressive. Failing to produce something good enough. It's not that he was married to that particular idea of what to do, that particular date, it's that he failed to be impressive and effortlessly produce something Haru liked. He's meant to be sweeping Haru off his feet, so his date ideas should be perfect and his gifts should be perfect and he should do everything completely right at all times.
Man, you really can fit so much anxiety in one person, huh.
And he's... sure Haru would like it if Jaeha could effortlessly guess the best way to woo him in a way that somehow didn't violate his privacy. Who wouldn't? But there isn't, actually, a way to do that. And the next best thing is asking, it's learning the hard way, with words, what things Haru likes. And it's also, partially, learning what Jaeha likes, and then... telling Haru that. So that they can figure it out together.