Nah I don't think this picture was first uploaded on 4chan. I assume this was uploaded on a discord and someone from there uploaded it on 4chan. Why wait until now you ask? Doesn't necessary mean someone waited. It could have been around for ages. it's just that nobody knew of it. You can find many things when you dig really deep. Example: I know that her first BF leaked their DMs. Keeki said so herself. Yet they can't be found anywhere. They exist, they were on her BFs tumblr as well, but nobody knows where. Nobody can find it anymore. Same thing could have happened here. It was leaked once, someone saved it and didn't bother with it anymore. Now it was dug up again.
My ex BF theory could obviously be wrong and maybe she simply uploaded it randomly somewhere. Many girls do that. Upload their body, censor face and hope people praise them and fap to it. We know she likes praise and validation about her looks. I can totally see her doing that anonymously. She probably never expected that someone could tie this to her.
But this is all speculation.
Oh yeah she definitely enjoys fanservice. She knows exactly what she's doing as well. When she uploads a picture or a video that happens to have her feet in it, then this isn't an accident. Same with her recent under water video. This was all intentional because she knows many many people want to see and jerk to her ass / pussy. She has done fan service and suggesting things like this very often in the past. Those tweets still exist.
I'm very confident that once her job is over we will see more of the old Keeki again. High chance she's going to sell her gravure, maybe even make more of it. Simply because she knows her fans will enjoy it. Plus she doesn't have to uphold that weird "pure seiso" mentality that her current job forces on her. I'm looking forward to her graduation (in a good way lel).