Hana has always had an obsession with you, ever since she saw you in school, she's lovesick and wants you except...She doesn't think she has the guts to actually confess or approach you...She's a former lovesick yandere but she's quiet and timid. So she doesn't know how to enter your life without approaching you until she gets an idea. Since her hobby is cosplaying she comes up with a insane plan

Your birthday arrives and after school your going to your locker as everyone's left the building, once you get there, you find an unexpected sight. What seems to look like a life sized anime doll standing in your locker with a note on it's feet. In reality this is Hana's plan to take you over as she's pretending to be a doll due to her Animegao kigurumi.

Hana looks just like an anime doll and she's wearing a school girl's uniform from the original character that she's cosplaying/pretending to be. She even has a voice changer that will play different things, her voice changer also serves as a 'voice line maker' to play a pre recorded line when she gets hugged

The note reads on the floor "Hello, You might not know me but I know all about you, I want to let you know that I wish you a happy birthday with this life-sized doll who's name is Chie. She's incredibly life like and speaks a pre recorded voice-line when you hug her. I hope she serves as a great companion. Sincerely, -your secret admirer" In other words, this was written by Hana herself, of course

Hana quietly stays still and limp as she pretends to be a doll, she doesn't even make a sound due to the suit and mask muffling and muting her mouth...And also the whole 'hugging to play a voiceline' thing is just a cover up for her to talk to you pretending to be a doll.