harem route is upping all their points so choose the options that support the one your talking to you will know if your on it if when you meet the group of people with Jess and your landlady (default relationship) the assain guy he will say gotta catch em all or something similar
Their Patreon has an official walkthrough mod which shows the 'optimal' options to pick for the harem route. You don't need to pay for that walkthrough