while the realism of bruising is as such, I'm thinking about the timeline and I'm pretty sure it's more than thatBruises last a while, a hickey can last up to a week or so, all those scratches definitely last longer, I feel like a lot of mangaka don't realize that so just have them last a day, so its most likely just more accurate and they are the ones from their last encounter
given that we've established that currently ch1 is a year ago by Sakakibara's statement, and that every time we've seen any amount of skin from these two there's always bruises and scratches all over, I'm highly confident that the 3-4 hate sessions we've been shown are not the whole story. these two are definitely hate fucking on regular basis, and I wouldn't be surprised if they haven't had uninjured skin in months