I kinda knew that "Haruka" was misleading, because it's a very gender neutral name these days, lmao. Sure, it's "feminine" and looks like traditionally "feminine" still at this point, but at this point of time and tons of manga read or anime watched, you know that "Haruka" is also a name that is used for men, too.
Well, and speaking about how clichés there are in this series so far, I have sensed this might be a thing:
His "Mizuno" fake last name he used in the engagement party is real, he comes form a wealthy family that happens to own the hospital (this is the reason why he is using "Akiho" as a fake name and his grandmother is calling him out because of that). He probably want to come clean with Dr. Shiiba
Also, let's be real - his "I had a crush on her for a long time" lie might be as true as well, lmao