so is kamidera an attention seeker?
Unless it's a case of shitty/shallow writing ... She's probably someone that used to nerdy that learned to pretty herself up and/or had a late-bloomer-type image change and suddenly got a bunch of attention from men and started riding the wave.
In a normal work, Her insistence on "you're trying to do this just to ask me out on a date" would be from her being swooned and tossed aside a few times due to her not used to being popular... but in an Otaku work like this, she likely just wants to be popular or is playing a role and is afraid of being exposed - but is of course completely pure and untouched!
She does have that weird childish "referring to myself in 3rd person" trait that can only exist in a work like this for a character her age, so maybe she's also supposed to be the Moe Stupid Type that just made it through life by being cute and going with the flow but somehow wasn't snapped up by an assertive man? Whatever.
Guess it would be funny if she thought acting kind of stupid is what it takes to be popular.
why do they all seem so interested in him now...
Because of the way times works in the other world he basically had a bunch of character development in a short span. So it’s like he had a huge change in personality overnight. If you had a coworker who was timid and lazy for years then show up one day super outgoing and hardworking it would be very strange and intriguing.
Glasses OL is probably a supervisor or on a leadership track (from the raws she seems to be close to the company leadership, maybe she's a bit older than the MC) and as such is interested in why/how the MC suddenly changed for a number of reasons, one such more personal reason could be that she's a Starving Office Lady Huntress looking to catch and finish off her prey of choice before "The Cakening" (also known as "Hitting The Wall" in the West).
But really, he's surprisingly competent, seemingly shares a common interest, and isn't tripping over himself to please her.
Probably the type of woman that was instructed on how to "see the underlying signs / traits of a good man." and MC is accidentally becoming a target rich environment.