I mean, if no one else knows she's married, why not just have a public "dating" relationship at the workplace. Unless the place of work has rules that govern such relationships, it would be above board for everyone else there and would not appear unnatural to see them together.
All these guys are going to be able to give the Batty speech now...
"I've seen things you people wouldn't believe. Giant wolf monsters tearing up demi-gods. An army of bugs creeping from the void getting eaten by Dragons. Attack ships on fire off the shoulder of Orion."
At this point, they'd be considered a common-law married couple in quite a few places. They better not sign anything for the other out of convenience or they may have to go through a divorce if one or the other ever moves out.
Good ending... not great, but good. Would have liked to see some closure on the President and Oka-kun, maybe a mention of their relationship or her disease.
I suspect, just spitballing here, she's going to twist him into trying to kill her husband... Just like Garth from Wayne's World II! Enters a "virgin", comes out a man, is handed a gun and told to go stop that evil husband of hers!
So, yeah... could happen?
I think that's where this will be going - she will ask him about it and if's he's able to put his fears into words she may help him understand what her actual expectations are and allay his fears.