Responses
I have an inkling sunbae remembers their past lives and something happened but that he found Yeon again in this life
Maybe its the consequence to ancient lil yeon messing with their fates. It’d affect the romance/dating aspect of their lives, since kihoon says his all fail after a month meanwhile yeon hasnt been in one (that we know of) so we arent sure on his side.
I think sunbae's bad luck when it comes to romance has something to do in the past too.