The specific thing they are doing right now is scary. It's not too scary to do at all, but Haru's ready to flinch about it, like if he were trying to pick up a snake that might wrap gently around his hand no problem but might strike; he is prepared to discover at any instant that actually he can't handle this and it's too vulnerable he isn't ready and he needs to lock down again.
On the topic of Jaeha in general, though, the way they're curled up together, that's very comfortable and fond and warm, maybe because he can flinch about the mental contact whenever he wants and everything else between them is definitely safe.
A little longer-term anxiety about Project Cut It Out Forever, it's surprisingly complicated - not very surprising but yes very complicated - but not in a way that has called into question whether it's worth undertaking and sticking around to see through.
Haru is maybe a bit lower on the somaticized emotions in general than most people. There's the faintest flickers of the correlates of other thoughts going by but they're happening almost entirely on a level Jaeha can't read, not because Haru's not letting him but because Jaeha's power doesn't extend in that more verbal direction. Tiny flecks of pride and curiosity and satisfaction that register in the nerves for only an instant before being packed away neatly as endorsed attitudes or dismissed passing fancies.