To be fair, while the whole idol thing is preventing the other sister from getting her man or screen-time for that matter, it was thanks to that that the guy fell for the sister in the first place.
Yuriko sucks anyways, like she's basically toying with him on the daily without pushing it. She also believes her idol career is more important that tatara, to the point where she forces him to date her sister. Honestly Ranka is best girl 100%
im telling you that it's going to end like nisekoi, where the girl he spent the longest time with will win in the end. if the author makes yuriko win without AT LEAST the the same amount of interaction time ranko had with mc I'll be very mad. at this point yuriko should just concede defeat and continue being an idol