Not sure what the title has anything to do with the plot. One of the yu is a pet so anon clearly didn't "met" two of them at once.
Maybe it refers to the other anon, the one who beat them up? But in that case that anon met 3 yu's since their ko is born by then.
Perhaps the one who crushed Marisa and the one who killed the Reimu-Ko are different anons?
Unless this get's translated, perhaps we'll never know the true meaning of the title...
Also this was uploaded on 7th October so it wasn't even uploaded on Halloween night
Oh yeah plot summary. It's just the usual pet refresh with stray, abandoned, yadda-yadda-yadda and they all die