Had a quick play through and I do like it. Looking forward to more!
On the technical side, I don't have anything to add besides what has already been said. There were a couple of grammar issues present but nothing near it being as bad as to be annoying.
Note that I've only played through once, on the nice guy path, so I can't say anything about the domination path that seems to exist.
Writing wise, it's too early to complain about Kari feeling too flat, but she does feel pretty passive. You're trying to portrait her as a sheltered girl that hasn't much experience with, well, anything. After a week of being bullied and harassed she should be overwhelmed and in need of some emotional support.
Personally, I'd really like to see the MC taking on more of a mentorship role. He's an experienced man and there's that young girl on her first adventure in the big city. My first reflex is to do everything I can to make her feel more comfortable, and that doesn't mean buying her shit or giving her money. (I can see that being the proper tactic for a grooming path of course, but not a romantic one. Make him walk all over HR instead!)
If you intent this to be a full blown game, the pacing needs to slow down a whole lot. I was perplexed when after a week I chose to let her stay in the apartment and... well guess we're a couple now. What? The main love interest needs to have a slow burn. Let them be friendly and slowly grow closer. Let him hook up with other LIs (I assume there will be others, with how Kari's friend was introduced.) Let them both slowly realize that they are feeling more for each other than just friendship, and throw some obstacles in their way - Maybe she started going out with some douche who only wants to get into her pants (You gonna get sooo much shit from the 'looking at other people is NTR!!!11'-crowd
) Maybe the MC hooked up with that flirty barista at Mike's. Clean up the second bedroom, you're already not going for the 'Oh no, there's only one bed!' thing. Have Kari be annoyed at being kept awake by the MC fucking the whole night.
Sorry, I'm rambling. See it as my recognition of the infinite potential this story has. But most importantly, tell the story you want to tell! There are many people here, with many opinions and mine is just one of them. If you want to work on this long term you need to be happy, even enthusiastic with what you're putting out. There'll always be an audience here for what you do, so don't try to make everyone happy.