[/m] It's about young man (high schooler if I'm not mistaken) who loves "cosplaying" after school, but no one knows it is him (but I forget what term for the habits of him, clearly, he likes to wear clothing that eccentric). Until one girl of his classmate found out that it is him, and he was invited to a club at the school. I just read 1 chapter, but completely forgot on most of the story and specially the title of this manga! Can anyone reminds me back please.....

I think you might be referring to Uwasaya.

I've checked that link, and.... EXACTLY RIGHT!!! It really made me wondering a hole day
Thank you clastine! 😁