while i don't remember exactly which chapter it should happen after you start the day by waking up late, after the night of the shooting, you'll get the choice to go for a run or sleep. for the asriel one while you go for dessert with him you'll get to choose where to go next (shopping, swan park, and books if i remember correctly) choose swan park.i did all routes so i know this works on all of them though there are some problems with them, except for the sans route. hope this helps!!