When you start reading a random comic or manga and then it turns out that not only is it sappy romance, but it is in fact sappy gay male romance, but at that point you have been swept by the plot and can't stop reading.
Not that this would be something that happens to me often.
Just twice. There was a third manga which turned out to be "boys love" series, but frankly, apart from few creative quirks it was quite boring so I didn't read far into it.