In all honesty though I don't think it's fair to invalidate fear or embarrassment like that. Having your fetishes exposed to a larger group, probably even being (playfully) made fun of one of your most vulnerable aspects can be very scarring, even if it's "harmless" like that. I mean as much as I love hypnosis with my heart and as much as the stuff here is so unrealistic and fantastical that it's playful and thus we view it as harmless, only a small fraction of the art here shows consensual sex with consensual or playful hypnosis. Most stuff on here is still technically rape, and we do have a lot of vore, bestiality and even lolis.
Really, just to be clear: I DO think this fetish is harmless, I do think it's not actual rape, I do see it as sub-fetish of the typical power fantasy that almost everybody has in some way or another. But that's because I'm inside here, I know the ins and outs of a hypno fetish and so on. To an outsider all of this here might look like actual rape.
But yeah, I didn't want to rant here, I wanted to actually be helpful. Having my hypnofetish found out is one of my fears too to be honest, and it's the obvious reason I'm using the hypnomaid-nickname in everything fetish-related.
So what if your friend found out? Changing your username might be appropriate, but it might also possibly put a nail in your coffin. If you are that embarrassed, delete this post and fill your account with personal info that is completely unrealistic, then use that as a proof that it's not really you and laugh about how someone chose the same username as you. If the account is already directly linked to you, blame it on being curious. Act super awkward, say something about a hot pic you saw from your favorite anime/video game character that was posted on "that weird hypnofetish site" and you had to make an account to see all of it and you were so curious (I mean hypnopics collective actually does that) or just do the classic "I made an account to comment". Maybe say you found a part of that pic on Twitter, then clicked on the source (here) and made an account to comment.
And that's only what you can do if you actually are ashamed. You can also just come clean completely, or, depending on how "strong" your fetishes are, come partially clean, play it cool, say something like "yeah, they have some pretty cute pics, I don't care if they are hypnotized".
If you are afraid to be labeled as weirdo who gets off to anime girls in front of your "normal" friends, then you should go with one of the former options.