If im not mistaken the romance barely start so far in the demo so if you see only a few romantic interactions with him then it's not you doing something wrong, its supposed to be that way! His route is kinda slow burn (not the slowest tho) so it may get a while to get there.
Ohh okay! Tysm cause I was really upset that this might've been another RO that I would be too dumb to romance since Helios was the first that caught my eye :D