All this talk about a walkthrough... You do know that there's literally only one brief section near the beginning where anything other than the top option is basically a 'no' to anything. If you want the full harem ending just pick the topmost answer.
The only caveat to this is where Maddy is getting help from the MC for the second time - THEN you'll need to know the answers. But then again, they're pretty simple.
At first I knew you had some minor shortcomings when it came to cars, as you couldn't even put the wheels on. But then it seemed like you learned absolutely everything while working at the car repair shop.
I haven't tried this game yet, still I check the front page from time to time when there is an update. And when I red "There are no animations" I smiled because I know what it also means.