While imagining scenario in my head i just realised something, even though when speaking omoi-san is "heavy", Karuizawa is actually MORE HEAVY than her. On one side omoi only talk about their future as a married couple, but him, he did jump from the 2nd floor without hesitation at all just to prove something to her father. Also even though omoi-san talk a lot about marriage, Karuizawa seem to already consider marriage as a guarantee, he didn't doubt it at any time. There are also other nuance that i feel lazy to write down
Well just an opinion but yeah, the heavier of the 2 is still Karuizawa