I mean, idk how the author wanted to progress with the plot but seems like this was a bit out of hand. The worst is Tsukasa worried about Yui keeping her fetish in the middle of this situation, then right after acting like scared of Yui reaction. The bond this girls will have seems to be far from anything wholesome.
So in the end were Yui friends that got jealous and cause this mess with the photo.
Btw, the author decision to use his death as development was taken lightly that even keeping his body intact after being run over by a train just for her to tie him seems ridiculous.