i believe Negi is the kind of author that writes a story based on a single scene/event, that's why some of the scene felt really off/weird..
the "parting" scene at ch120 is the biggest offender for me with the fact that 2 chapters latter, it revealed that they went graduation trip together and also honeymoon trip together, with lots more trip together in between, the fact that Futaro and Yotsuba is dating, make that scene even weirder..
the "last quint game" also weirdly placed (its cute, just not the right time and place)
the "biological father", and some more..