You have never understood how people in a relationship can seriously quarrel, that this is nonsense and such people simply do not know how or do not want to discuss problems calmly. At least until the quarrels started in your relationship with Nanami.

"You're insufferable," Kento grumbles too loudly, frowning his thin eyebrows.

You won't remember what caused the quarrel this time: everything happened too quickly, both of them flared up, it seems, out of the blue, switching to raised tones and even a couple of insults.