So far how's Jiwoo relationship?? With who's sister was it??

And is there any romance cause it spoils the mood for me... I stopped halfway after Jiwoo and that who's older sister was it get close enough for me to assume they have a thing for each other tiny bit! I'm sorry to bother but I just don't like reading romance in between of a good adventure comic so if you don't mind please let me know how's it so far!? I'm fine with spoilers