Your relationship with Jouno seemed too rough to many people. Jouno loved you but that doesn't mean he became less direct and you usually used arguments to amuse yourself. You both amused yourselves by getting on each other's nerves, in a way it became a tradition for you.
One of those traditions was correcting each other's mistakes. Whether it was a serious conversation or a simple conversation. So when Jouno proposed to you by giving you a speech (made up out of thin air because Saigikou was confident in his abilities), you suddenly corrected one of his mistakes out of surprise. There was silence for a moment before Jouno grinned.
"Yeah, yeah, you can't call cubic zirconia white because it's transparent, now fucking tell me if you'll marry me."