Well first of all that was the last time for him to see her and he was obviously trying to confess. Wanting to get that out is something entirely reasonable, there are a lot of people in the world that confess even though the other person is married or some shit. Idk how many manga you read but seeing by your pfp and name probably a lot. So I ask you this question: Have you ever noticed that it is a thing in japan for men to bring girls back home, even if they are just aquainted. Hell even in western society it was and sometimes still is a thing sometimes. Additionally to that they've been co-workers for probably years so they actually somewhat know each other, she never told him to not go with him, nor did she tell him directly off.
Not saying he overdid it and could've handled that better, but I am saying he wasn't that bad, not that he was good or anything.
Also you say fake or not. Now there is a difference between knowing that you've been turned down cus of a boyfriend or because someone made an excuse, especially considering self-confidence and validation. So if you don't tell someone that you don't want them around then there is far worse than just wanting to spend a couple more minutes together with your crush and sending them save home before parting forever.
Also just saying but she was also not the most adult in that situation. When you know a confession is comming your way or you know somone is interested in you, then just shoot them down, tell them clearly you want nothing to with them, everything else just makes it harder for the other person and yourself.
She should've simply taken that 30 minute 1 on 1 conversation and have clearly told him no. Or should've just clearly stopped him at the train. But everything thats not a clear no gives people hope, especially considering there are girls out there that want the men to try a bit harder so to say. Someone told me that a girl they asked out turned them down, just to later comeback and be angry at them for not asking said girl out a second time cus she wanted to see them try. Which is utter bullshit, no is no and not taking a no as a no even if you think its not meant seriously is not ok and should not be done like ever, but still, shit like that happens.
Anyway unless properly told off there is nothing bad about trying to spend a couple more minutes with ones crush to see them of properly, so one knows they did everything they could and had a clean ending. Now he did get angry at the end which is like bad, but he left after that, so thats just an emotional reaction that some people have. All in all considering how other people may react that is pretty darn tame and also human
He was already angry before then and still followed her into the train. If anything, by the end he was barganing, desperate. He didn't "leave after that" (being angry), he left after a man appeared.
It didn't start so cataclysmically bad: it's reasonable to argue that touching someone as they lose their balance, even if its in a place it'd normally not be okay to touch a stranger, ought to fall under the protection of a good samaritan law; he missed her silent queues when he first tried to brought it up but they were suddenly interrupted; Its not unreasonable that someone would look for a ring/ keep an ear out for a confirmation of a partner/ask a mutual acquaintance before making a move.
But then he fails to notice her dodging his question and forces himself to accompanny her, even after multiple refusals, and the way he categorically states he's "been watching her" and "knows she doesn't have a bf" are all red flags. Losing your temper when things don't go your way is a huge one. Alcohol doesn't excuse it, it only speeds up the process.
Is it possible for me to insist after a "fake no" and manage to pull a victory out of the jaws of defeat? Yes but its my neck on the line:
if I did read the situation properly, I'm on my way to a happily ever after,
if not, I
am a creep. It's no small gamble and leaves an innocent party exposed to an unconfortable and often scary situation.
Few stories ever acknowledge, let alone delve into how unconfortable it can be when someone you don't know "confesses their love": you have no attachment to that person, you might feel no attraction and they tell you they've been keeping an eye on you?
Even if it's a harmless, genuine crush, the person on the receiving end can't know that. It's not always a compliment.
No one's entitled to take a load off their chest because no one's required to put up with it and listen against their will.
You have to consider that intention only counts for so much in interactions with strangers/acquaitances: the other party's interpretation of what happens (outside your inner monologue) has it's own weight and so does properly taking that into account (or not), i.e. empathy.
What he did was bad: he came across bad, he put her in a spot publically, he insisted into accompanying her home and he didn't think about how any of that made the individual on the receiving end feel.