Okay, here is the thing about this manga: it acts like it's very clever but it's actually pretty unrealistically dumb:
First of all Editorial would never hire an assistant just before the deadline... unless you have a bad reputation and really needed help! Otherwise she is just a distraction which she ended up being.
Second, you can bet your arse that in the era of free communication, your editor would call you or text you: "hey, the deadline is coming. When can I expect that manuscript?" Or "We are having a meeting tomorrow, bring the manuscript" or "you missed the deadline yesterday, what happened?"
No one would just let you off tbe hook for that!
Second, MC is a disaster... this manga is belongs to the gal and he is basically a piece of luggage along for the ride...