I did this spread during my lunch hour. Trust me, the spreads are not digging into the time we reserve for manga chapters. We plan on releasing the whole magazine, and with it comes the occasional spreads that work as sneak-peaks and wallpapers for upcoming chapters.
There's a panel or two where he is shoving it between her breasts while shoving it into her mouth. I'd call that tit fucking. But eh, to each their own.
The humiliation tag specifically states "often be forced upon them unwillingly", so it's not always forced upon them, sometimes, like in this case, it's willingly. This particular lady though gets off on the possibility of humiliation itself, and the risk of ruining her job and reputation, and was the main theme of the story.
Using a dildo isn't the same as no longer being a virgin. The one girl states she uses toys. Being a virgin means you finally commit the sexual act with someone else, which, for some people, first time is super awkward.