Ok, I thought their dads were friends or at least friendly acquaintances. Isn't that how the whole thing got kicked off? Girls' dad was looking for a tutor and Fuutarou's dad offered his son? Maybe I need to re-read it. Not sure why there seems to be bad feeling there.
Also, this whole "winning a lottery at the same time" is a little too contrived for me, but if it's actually all part of the dad's scheme, I'm sure he could have pulled off rigging the whole thing. The only question is what is he trying to pull? He seems to be deliberately flaunting his renewed relationship with his daughters but beyond that I can't tell.
Also, will Fuutarou realize that the seedy-looking, new tutor their dad supposedly hired (girls' fib a while back) is actually the family butler?