The rules I see myself having a problem with are rules for creating romance. Most game engines can handle casual flirting, but leave actual romantic love up to the players without specific rules for how they happen. Is this different for games like Thirsty Sword Lesbians have rules for this, or is the romance itself a preexisting condition? I see problems with consent here, should a game engine really be telling me who I fall in love with?
Should a game engine be telling you how close you are to killing a baby were-seal?
So step 1 is get player consent.
Step 2: grab yourself a free copy of Modos 2, and prepare to dive into the Extended Conflict module (don't worry, it's only at a rules-count of 30-40).
Step 3: try to guess your crush's Goal. It could be anything, so some deeper-than-smalltalk conversation might be needed. Alternatively, if Metaphysical isn't your strong attribute (you'll be needing it later), you could probe your crush's acquaintances for clues, possibly using Mental or Physical contests for these.
Step 4: use your skillz! As often as the GM allows (probably once per scene), do something you'd hope aligns with your crush's goal, with a Metaphysical contest. If your crush a) finds you unattractive (looking at you, gnomes), or b) has a reason to avoid your advances, the crush opposes your contests with Metaphysical (willpower by default).
Step 5: get a clue! The GM tells you how close you are to guessing the crush's goal by assigning a progress die to your Pro contest (a Con doesn't make progress). Get a d4, and you're way off. Get a d12 and you're dead-on! The crush agrees to holy (or unholy) matrimony when you reach max progress. Note: this use of extended conflict assumes the PC will win eventually. So it's not a conflict of whether, so much as a conflict of when.
WARNING: if you win your crush's heart in one or two contests . . . it's probably too good to be true. "What if she's a zombie or a Dracula? I better hang on to this (gat)."