This is pretty much what happened to my character Calil, where she was normally extroverted until she joined the Great Demon Wars. If you want me to discuss more on Calil, you can say so.
Also, is that Mimic? Girl, you should know better than to trust him. I get this is a flashback, but still.
Also also, as a member of the Splatoon fandom, this is pretty much what (is implied to have) happened to Captain 3.