I've been on a Mochi binge today and I just finished reading Met My Sister on a Dating Site. I actually read Yuri Natsu (all 78 chapters) before it and seeing how Tsubomi changed in Dating Site made wonder: what the hell happened to her?! I felt so sad seeing how aggressive she got but deep down I could tell she was suffering big time.
My guess is that in the current Yuri Natsu timeline something must have happened and I can't wait to find out what.